Heat exchanger and refrigeration cycle device using the same

ABSTRACT

An object is to improve a pressure resistance and a thermal performance of a heat exchanger and to provide the heat exchanger suitable for use in a refrigeration cycle device in which carbon dioxide is used as a refrigerant. The evaporator (the heat exchanger) includes a pair of plate materials, the whole periphery of a peripheral portion of an outer plate as at least one of the plate materials is secured to the other plate material constituting a bottom surface of an inner tank to constitute a sealed refrigerant passage space between the plate materials, a portion of the outer plate other than the peripheral portion is provided with a plurality of secured inner portions which are secured at predetermined intervals to the bottom surface, and a plurality of refrigerant inlet tubes and refrigerant outlet tubes are attached so as to communicate with the refrigerant passage space.

BACKGROUND OF THE INVENTION

The present invention relates to a heat exchanger. The present inventionmore particularly relates to a heat exchanger for use in a refrigerationcycle (vapor-compression refrigeration cycle) device in which arefrigerant circuit including a compressor, a condenser (or gas cooleror condensing heat exchanger or gas cooling heat exchanger), athrottling means and an evaporator is constituted and in which carbondioxide is introduced as a refrigerant, and a refrigeration cycle deviceusing the heat exchanger.

Heretofore, in a refrigeration cycle device in which a refrigerantcircuit including a compressor, a condenser, a throttling means and anevaporator is constituted, a fluorocarbon-based refrigerant has broadlybeen used. However, in recent years, this type of refrigerant cannot beused owing to global environment problems such as prevention of ozonelayer destruction and prevention of global warming, and attempts to usecarbon dioxide as the refrigerant instead of the fluorocarbon-basedrefrigerant have been made.

In a refrigeration cycle device in which a carbon dioxide refrigerant isused, a pressure of the refrigerant circuit remarkably increases ascompared with a case where the conventional fluorocarbon-basedrefrigerant is used. Therefore, as each unit (the compressor, thecondenser, the throttling means, the evaporator and the like)constituting the refrigerant circuit, a unit capable of bearing such ahigh pressure needs to be used. On the other hand, a theoreticalcoefficient of performance of the carbon dioxide refrigerant in therefrigerant circuit is remarkably lower than that of the conventionalfluorocarbon-based refrigerant. Therefore, a heat exchanger having ahigh thermal performance is demanded (see, e.g., Japanese PatentApplication Laid-Open No. 2005-37054).

However, to bear such a high pressure of the carbon dioxide refrigerant,a thickness of each member constituting the heat exchanger needs to beincreased, but this causes a problem of an increasing thermal conductionloss. Especially, in a case where the heat exchanger is constituted ofan evaporator to cool an object to be cooled stored in a cooling vesselfrom the outside of the cooling vessel, it has been difficult for such astructure of the heat exchanger to bear the high pressure of the carbondioxide refrigerant and secure the high thermal performance. That is,when the member constituting the evaporator is thickened so as to bearthe high pressure of the carbon dioxide refrigerant, the thermalconduction loss further increases. As a result, a problem occurs thatthe thermal performance remarkably deteriorates as compared with theevaporator in which the conventional refrigerant is used.

Moreover, as another method of securing a high pressure resistance, itis considered that a round tube formed so as to have an excellentstrength is used as a refrigerant passage of the evaporator. However, ina portion where the round tube comes into contact with the coolingvessel in which the object to be cooled is stored, a contact heatresistance increases. Therefore, such remarkable deterioration of thethermal performance cannot be avoided.

SUMMARY OF THE INVENTION

Therefore, the present invention has been developed to solve a problemof such a conventional technology, and an object thereof is to improve apressure resistance and a thermal performance of a heat exchanger and toprovide the heat exchanger suitable for use in a refrigeration cycledevice in which carbon dioxide is used as a refrigerant.

A heat exchanger of a first invention is characterized by comprising: apair of plate materials, the whole periphery of a peripheral portion ofat least one of the plate materials is secured to the other platematerial to constitute a sealed refrigerant passage space between theplate materials, a portion of the one plate material other than theperipheral portion is provided with a plurality of secured innerportions which are secured at predetermined intervals to the other platematerial, and a plurality of refrigerant inlet tubes and refrigerantoutlet tubes are attached so as to communicate with the refrigerantpassage space.

Moreover, the heat exchanger of a second invention is characterized inthat in the above invention, the secured inner portions are arranged atthe predetermined intervals in a checkered form or a zigzag form.

The heat exchanger of a third invention is characterized in that in theabove inventions, the refrigerant inlet tubes communicate with therefrigerant passage space in the center of the refrigerant passagespace, and the refrigerant outlet tubes communicate with the refrigerantpassage space in a peripheral portion of the refrigerant passage space.

A refrigeration cycle device of a fourth invention is characterized inthat a refrigerant circuit including a compressor, a condenser, athrottling means and an evaporator is constituted, the heat exchangeraccording to any one of the first to third inventions is used as theevaporator, carbon dioxide is introduced as a refrigerant, and asupercritical pressure is obtained on a high-pressure side.

The refrigeration cycle device of a fifth invention is characterized inthat in the fourth invention, the surface of the other plate materialopposite to the one plate material constitutes a wall surface of apredetermined space to be cooled, and the surface of the one platematerial opposite to the other plate material is provided with apredetermined insulation structure.

According to the present invention, the heat exchanger comprises a pairof plate materials. The whole periphery of the peripheral portion of atleast one of the plate materials is secured to the other plate materialto constitute the sealed refrigerant passage space between the platematerials. Moreover, the portion of the one plate material other thanthe peripheral portion is provided with the plurality of secured innerportions which are secured at the predetermined intervals to the otherplate material. Therefore, for example, after the whole periphery of theperipheral portion of the one plate material is secured to the otherplate material, a pressure is applied between the plate materials. Inconsequence, the refrigerant passage space is swelled and formed betweenthe plate materials. Therefore, where a pressure resistance of the heatexchanger is secured, a thermal performance of the refrigerant can beimproved.

Moreover, since the plurality of refrigerant inlet tubes and refrigerantoutlet tubes are attached so as to communicate with the refrigerantpassage space, pressure losses of the refrigerant at an inlet and anoutlet of the heat exchanger can be reduced while securing the pressureresistance of portions of the heat exchanger bonded to the refrigerantinlet tubes and the refrigerant outlet tubes.

Furthermore, when the secured inner portions are arranged at thepredetermined intervals in the checkered form or the zigzag form, thepressure resistance of the heat exchanger can be improved withoutincreasing thicknesses of the one plate material and the other platematerial.

In addition, according to the present invention, the refrigerant inlettubes communicate with the refrigerant passage space in the center ofthe refrigerant passage space, and the refrigerant outlet tubescommunicate with the refrigerant passage space in the peripheral portionof the refrigerant passage space. Therefore, since the refrigerantentering the refrigerant passage space from the center flows so as tospread to the peripheral portion, the refrigerant obtains a satisfactorydiversion property. Stagnation of the refrigerant in the heat exchangercan be prevented or eliminated as much as possible.

Since the heat exchanger of the present invention has an excellentpressure resistance, the heat exchanger can be used as the evaporator ofthe refrigeration cycle device in which carbon dioxide is introduced asthe refrigerant. In consequence, it is possible to improve a performanceof the refrigeration cycle device in which the carbon dioxiderefrigerant is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic constitution diagram of a refrigeration cycledevice of one embodiment to which the present invention is applied;

FIG. 2 is a sectional view showing a schematic structure of a coolingvessel;

FIG. 3 is a sectional view showing a schematic structure of anevaporator formed integrally with the cooling vessel;

FIG. 4 is a schematic constitution diagram of the evaporator;

FIG. 5 is a schematic constitution diagram of a refrigeration cycledevice according to another embodiment of the present invention;

FIG. 6 is a schematic constitution diagram of an evaporator according toanother embodiment of the present invention; and

FIG. 7 is a diagram showing one example of a result of a destructivepressure test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a heat exchanger of the present invention and arefrigeration cycle device including the heat exchanger will hereinafterbe described in detail with reference to the drawings.

Embodiment 1

A refrigeration cycle device of the present embodiment is one exampleapplied to a device which cools and insulates milk immediately afterdrawn until the milk is shipped. FIG. 1 is a schematic constitutiondiagram of the refrigeration cycle device of one embodiment to which thepresent invention is applied. A refrigeration cycle device 1 of thepresent embodiment is provided with a refrigerant circuit 2 constitutedby connecting a compressor 10, a condenser (condensing heat exchanger orgas cooler or gas cooling heat exchanger) 11, an expansion valve 14 as athrottling means and an evaporator 16 in an annular form via pipes so asto form a closed circuit. That is, a high-pressure refrigerant pipe 40connected to the compressor 10 on a discharge side is connected to aninlet of the condenser 11. The condenser 11 is a heat exchanger whichperforms heat exchange between a refrigerant and a heat medium torelease heat of the refrigerant to the heat medium. It is assumed in thepresent embodiment that air is used as the heat medium and that the heatexchange between air blown by a fan 11F and the refrigerant isperformed.

Moreover, a refrigerant pipe 41 connected to an outlet of the condenser11 is connected to an inlet of the expansion valve 14. The expansionvalve 14 is the throttling means to reduce a pressure of the refrigerantwhich has rejected (transferred) the heat in the condenser 11, and arefrigerant pipe 42 connected to an outlet of the expansion valve 14 isconnected to an inlet of the evaporator 16. Moreover, an outlet of theevaporator 16 is connected to one end of a suction pipe 45, and theother end of the suction pipe 45 is connected to the compressor 10 on alow-pressure side (a suction portion). Along the suction pipe 45 whichconnects the evaporator 16 to the compressor 10 on the low-pressureside, an accumulator 17 is interposed which protects the compressor froma disadvantage that a liquid refrigerant is sucked into the compressor10 to damage the compressor or the like. Furthermore, between theevaporator 16 of the suction pipe 45 and the accumulator 17, a checkvalve 18 is disposed in which a compressor 10 side (an accumulator 17side) is a forward direction in order to prevent a disadvantage that therefrigerant flows back to the evaporator 16 from the refrigerant circuit2 on a high-pressure side.

Furthermore, a discharge temperature sensor T1 which detects atemperature of the high-temperature high-pressure refrigerant dischargedfrom the compressor 10 is disposed at the high-pressure refrigerant pipe40. An evaporation temperature sensor T5 which detects an evaporationtemperature of the refrigerant in the evaporator 16 is disposed at theevaporator 16 or the refrigerant pipe 42. Furthermore, a suckedrefrigerant temperature sensor T7 which detects a temperature of therefrigerant entering the compressor 10 from the evaporator 16 isdisposed at the suction pipe 45.

In addition, carbon dioxide which is a natural refrigerant is introducedas the refrigerant in the refrigerant circuit 2. Since the pressure ofthe refrigerant circuit 2 on the high-pressure side rises in excess of acritical pressure, the refrigerant cycle is a trans-critical cycle. As alubricant of the compressor 10, for example, mineral oil, alkyl benzeneoil, ether oil, ester oil, polyalkylene glycol (PAG), polyol ether (POE)or the like is used.

On the other hand, the evaporator 16 is a heat exchanger which cools anobject to be cooled (milk in the present embodiment) stored in an innertank 70 of a cooling vessel 7, and is formed integrally with thiscooling vessel 7. Here, the cooling vessel 7 of the present embodimentwill be described in detail with reference to FIGS. 2 to 4. FIG. 2 is asectional view showing a schematic structure of the cooling vessel 7;FIG. 3 is a sectional view showing a schematic structure of theevaporator 16 formed integrally with the cooling vessel 7; and FIG. 4 isa schematic constitution diagram of the evaporator 16, respectively. Thecooling vessel 7 is provided with the inner tank 70 having apredetermined space to be cooled in which the object to be cooled (themilk) is stored in an outer tank 72 constituting an outer shell of thecooling vessel 7. An outer plate (one plate material) 76 constituted ofa plate material having a high thermal conductivity is disposed on anouter surface (a bottom surface 70B in the present embodiment) of theinner tank 70. The whole periphery of a peripheral portion of the outerplate 76 is secured to the other plate material constituting the bottomsurface 70B, and a sealed refrigerant passage space 77 is constitutedbetween the plate materials (the bottom surface 70B of the inner tank 70and the outer plate 76). It is assumed that this space is a refrigerantchannel of the evaporator 16 (FIG. 3).

In this case, the surface of the other plate material (the bottomsurface) 70B opposite to the outer plate (the one plate material) 76constitutes a wall surface of the predetermined space to be cooled inwhich the object to be cooled (the milk) is stored, and the surface ofthe outer plate 76 opposite to the bottom surface 70B as the other platematerial is provided with a predetermined insulation structure. That is,in cooling vessel 7 of the present embodiment, a space between the innertank 70 including the surface opposite to the bottom surface 70B of theouter plate 76 and the outer tank 72 is filled with the an insulationmaterial 74 constituted of a foaming material such as urethane. Aftersecuring the outer plate 76 to the inner tank 70 and further assemblingthe outer tank 72 on an outer side of the outer plate, the insulationmaterial 74 is injected into the space between the inner tank 70 and theouter tank 72.

Moreover, a portion of the outer plate 76 other than the peripheralportion is provided with a plurality of secured inner portions 78 whichare secured at predetermined intervals to the bottom surface 70B (FIGS.3 and 4). Specifically, the whole periphery of the peripheral portion ofthe outer plate 76 is secured to the bottom surface of the inner tank 70by seam welding, and the portion other than the peripheral portion issecured at predetermined intervals in a checkered form or a zigzag formby spot welding (the portions secured by the spot welding are thesecured inner portions 78).

Here, the refrigerant channel (the refrigerant passage space 77) of theevaporator 16 is processed by pressurizing. Specifically, after thewhole periphery of the peripheral portion of the outer plate 76 and thesecured inner portions 78 are secured to a bottom portion of the innertank 70 as described above, a pressure is applied between the inner tank70 and the outer plate 76. In consequence, the refrigerant passage space77 is expanded and formed between the inner tank 70 and the outer plate76. Therefore, portions other than the secured inner portions 78 of theouter plate 76 swell outwards substantially into circular sections(downwards in FIGS. 2 and 3), and a large number of swelled portions arecontinuously formed in the checkered form or the zigzag form.

The bottom surface 70B of the inner tank 70 secured to the outer plate76 is constituted of a material having a high thermal conductivity inthe same manner as in the outer plate 76 so that heat exchange betweenthe refrigerant flowing through the refrigerant channel (the refrigerantpassage space 77) of the evaporator 16 and the object to be cooled (themilk) stored in the inner tank 70 is easily performed. It is preferablethat a material of the inner tank 70, the outer plate 76 and the outertank 72 is selected in consideration of corrosion, durability and thelike. For example, as the material of the inner tank 70, the outer plate76 and the outer tank 72, a stainless steel may be used.

Moreover, as a shape of the cooling vessel 7, various shapes such as acolumnar shape, a horizontally disposed elliptic columnar shape and arectangular parallelepiped shape are considered, but it is assumed inthe present embodiment that the cooling vessel has the horizontallydisposed elliptic columnar shape. It has been described in the presentembodiment that the outer plate 76 is disposed on the bottom surface 70Bof the inner tank 70 to form the refrigerant channel (the refrigerantpassage space 77) of the evaporator 16 so that the object to be cooled(the milk) can efficiently be cooled, but the outer plate may further beformed on a side surface of the inner tank 70 if necessary. It is to benoted that as not shown in FIG. 2 for the sake of simplicity of thedrawing, the cooling vessel 7 is provided with an introduction port 7Afor introducing the object to be cooled (the milk) and a takeout port 7Bfor taking out the object to be cooled (the milk) (FIG. 1).

Furthermore, a plurality of refrigerant inlet tubes 16A and refrigerantoutlet tubes 16B are attached to the refrigerant passage space 77 (therefrigerant channel of the evaporator 16) formed between the bottomsurface 70B of the inner tank 70 and the outer plate 76 so that thetubes communicate with the refrigerant passage space 77. The refrigerantinlet tubes 16A allow the refrigerant to enter the evaporator 16 (therefrigerant passage space 77), and one end of each refrigerant inlettube is connected to the refrigerant passage space 577. The other end ofthe refrigerant inlet tube 16A is connected to the refrigerant pipe 42so that the refrigerant is branched from the refrigerant pipe 42 to therefrigerant passage space 77. The refrigerant outlet tubes 16B dischargethe refrigerant from the evaporator 16 (the refrigerant passage space77), and one end of each refrigerant outlet tube is connected to therefrigerant passage space 77. The other end of the refrigerant outlettubes 16B is connected to the suction pipe 45 so as to combine therefrigerant from the refrigerant outlet tubes 16B.

In the cooling vessel 7 of the present embodiment, the inner tank 70 hasa plate thickness of 2 mm, and the outer plate 76 has a plate thicknessof 1 mm. Each of the spot-welded portions (secured inner portions 78)has a diameter of 6 mm, and it is preferable to set a spot pitch (aninterval from the center of a certain secured inner portion 78 to thecenter of another secured inner portion 78 adjacent to the certainsecured inner portion 78) to 20 mm or less so as to bear use of thecarbon dioxide refrigerant. A specific method of determining the spotpitch will be described later. In the present embodiment, the spot pitchis set to 18.5 mm. It is preferable that an outer diameter of each ofthe refrigerant inlet tube 16A and the refrigerant outlet tube 16B is ½or less of the spot pitch in order to prevent deterioration of strengthof a tube bonding portion. In the present embodiment, the outer diameteris set to φ6.35 mm (¼ inch), and the plate thickness is set to 1.0 mm.

Moreover, in the present embodiment, as shown in FIG. 4, the refrigerantpassage space 77 is constituted of two parallel refrigerant channelsobtained by dividing a region into two regions at the center by seamwelding. That is, the vicinity of the center of the outer plate 76 issecured to the bottom surface 70B of the inner tank 70 by the seamwelding so that the refrigerant passage space 77 formed by securing thewhole periphery of the peripheral portion of the outer plate 76 to thebottom surface 70B of the inner tank 70 by the seam welding as describedabove is divided into two independent regions (two upper and lowerregions in FIG. 4). In consequence, the refrigerant passage space 77 isformed into two parallel refrigerant passages, and the refrigerant fromthe refrigerant pipe 42 is branched via the refrigerant inlet tubes 16Ato enter the refrigerant passages.

It is to be noted that the refrigerant passage space 77 constituting therefrigerant channels of the evaporator 16 is divided by the seam weldingand can arbitrarily be constituted. In the present embodiment, theregion is divided in the vicinity of the center to form the refrigerantpassage space into two paths (two refrigerant passages). However, theregion may constitute one path without being divided as in the presentembodiment. As another method, the region may finely be divided toconstitute three, four or more paths. Furthermore, the refrigerantpassage may be formed into a meandering form or a spiral form by theseam welding.

Next, a processing method of the evaporator 16 will be described indetail. First, a flat plate material as a material of the inner tank 70is pressed and cut into a predetermined size. Similarly, a flat platematerial as a material of the outer plate 76 is pressed and cut into apredetermined size.

Next, a plurality of holes are processed beforehand in the outer plate76, the holes constituting refrigerant inlets to be connected to therefrigerant inlet tubes 16A and refrigerant outlets to be connected tothe refrigerant outlet tubes 16B. The outer plates 76 are superimposedupon a position where the bottom surface 70B of the plate material ofthe inner tank is to be formed. The outer plate 76 is secured by thespot welding with spots made at the predetermined intervals in thecheckered form and zigzag form. In consequence, the outer plate 76 isprovided with the plurality of secured inner portions 78 secured at thepredetermined intervals to the plate material constituting a bottomportion of the inner tank 70. Subsequently, the whole periphery of theperipheral portion of the outer plate 76 is secured to the bottomportion of the inner tank 70 by the seam welding, and further secured bythe seam welding so as to form predetermined refrigerant passages asneeded. In the present embodiment, as described above, the vicinity ofthe center of the outer plate 76 is secured to the plate materialconstituting the bottom surface 70B of the inner tank 70 by the seamwelding to form two parallel refrigerant passages.

Next, the plate material of the inner tank 70 to which the outer plate76 is attached is formed into such a predetermined shape to form theinner tank 70 by roll processing or press processing. In the presentembodiment, since the inner tank has a horizontally disposed ellipticcolumnar shape as described above, the flat plate material is rolled andbent by the roll processing. Subsequently, the material is welded andbonded to another member processed into a predetermined shape to formthe inner tank 70.

One end of each of the refrigerant inlet tubes 16A and refrigerantoutlet tubes 16B is welded and bonded to each of the plurality ofrefrigerant inlet and outlet holes made beforehand in the outer plate 76attached to the inner tank 70 processed into a predetermined tank shapeas described above. Secured inner portions 78P closest to bondedportions of these refrigerant inlet tubes 16A and refrigerant outlettubes 16B are again welded from an outer plate 76 side to reinforce thetank.

It is to be noted that the refrigerant inlet tubes 16A or therefrigerant outlet tubes 16B are substantially bonded between the spotswelded at the predetermined intervals in the checkered form or thezigzag form. Therefore, four secured inner portions 78P for reinforcingthe tank as described above are disposed for each of the refrigerantinlet tubes 16A or the refrigerant outlet tubes 16B (FIG. 4).

Subsequently, a pressurizing fluid is injected from the refrigerantinlet tubes 16A or the refrigerant outlet tubes 16B to apply a pressureto a space formed between the inner tank 70 and the outer plate 76. Inconsequence, the portion of the outer plate 76 other than the securedinner portions 78 is deformed outwards into a substantially circularsectional shape to form the refrigerant passage space 77. Here, in acase where a plurality of (two paths in the present embodiment)refrigerant passages of the evaporator 16 are formed as in the presentembodiment, it is preferable to simultaneously apply the pressures toall of the refrigerant passages in order to prevent deviatingdeformation.

It is to be noted that it has been described in the present embodimentthat the inner tank 70 is secured to the outer plate 76 by the spotwelding and the seam welding, but a securing method is not limited tothis example. The securing can be performed by another method such aslaser welding.

On the other hand, an introduction pipe (not shown) is detachablyconnected to the introduction port 7A of the cooling vessel 7 into whichthe object to be cooled (the milk) is introduced via an introductionport valve. Similarly, a takeout pipe for taking out the milk isdetachably connected to the takeout port 7B via a takeout valve.Moreover, the introduction pipe is attached to the introduction port 7Ain an only case where the object to be cooled (the milk) is introducedinto the inner tank 70 of the cooling vessel 7. In another case, thepipe is detached from the introduction port 7A, and the introductionport 7A is hermetically closed. Similarly, the takeout pipe is attachedto the takeout port 7B in an only case where the object to be cooled(the milk) is taken out of the inner tank 70 of the cooling vessel 7. Inanother case, the pipe is detached from the takeout port 7B, and thetakeout port 7B is hermetically closed.

Moreover, the cooled object temperature sensor T5 for detecting thetemperature of the object to be cooled (the milk) is attached to theouter peripheral surface of the inner tank 70 of the cooling vessel 7.Furthermore, the cooling vessel 7 is provided with a stirrer (not shown)which stirs the object to be cooled (the milk) in order to promote heatconduction during cooling, reduce temperature unevenness of the objectto be cooled (the milk) stored in the inner tank 70 and perform correcttemperature measurement.

Next, an operation of the refrigeration cycle device 1 of the presentembodiment constituted as described above will be described.

(1) Operation During Cooling Operation

First, an operation to cool the milk as the object to be cooled during acooling operation will be described. A milking pipeline connected to amilking machine (not shown) is connected to the introduction port 7A ofthe cooling vessel 7 via an introduction pipe (not shown), theintroduction port valve is opened, and the milk immediately after drawnis introduced into the cooling vessel 7. At this time, the takeout valveis completely closed, and the takeout port 7B is also hermeticallyclosed. A temperature of the milk immediately after drawn issubstantially equal to or slightly lower than a body temperature of acow, and is specifically in a range of about 35° C. to 38° C. Then, therefrigerant circuit 2 is operated to cool and insulate the milk for thepurpose of preventing generation of bacteria and maintaining a qualityof the milk.

After starting the milking (after starting the introduction of themilk), the compressor 10 of the refrigerant circuit 2 is driven, and thestirrer (not shown) is simultaneously driven. Usually, it is assumedthat after a predetermined amount of milk is stored in the coolingvessel 7, the compressor 10 is driven to start the cooling operation.However, the cooling operation may be started simultaneously with thestart of the introduction of the milk or before the introduction of themilk as long as careful consideration is given so as to prevent freezingand idling of the stirrer is prevented.

When the compressor 10 is driven, a low-temperature low-pressurerefrigerant gas is sucked and compressed on the low-pressure side (thesuction portion) of the compressor 10 from the suction pipe 45. Inconsequence, the refrigerant gas which has obtained a high temperatureand a high pressure enters the high-pressure refrigerant pipe 40 fromthe discharge side, and is discharged from the compressor 10. At thistime, the refrigerant is compressed under an appropriate supercriticalpressure.

The high-temperature high-pressure refrigerant discharged from thecompressor 10 enters the condenser 11 via the high-pressure refrigerantpipe 40. Here, the refrigerant releases the heat to air, and is cooledat a low temperature by ventilation of the fan 11F. At this time, sincethe pressure of the refrigerant is not less than a supercriticalpressure in the condenser 11, the refrigerant is not condensed.Therefore, the temperature of the refrigerant gradually lowers from theinlet toward the outlet of the condenser 11 as the heat is rejected tothe air. Moreover, at the outlet of the condenser 11, the refrigerant isbrought into a liquid-phase state usually having the pressure which isnot less than the critical pressure (or above the critical pressure).

Moreover, the low-temperature high-pressure refrigerant discharged fromthe condenser 11 passes through the refrigerant pipe 41. The pressure ofthe refrigerant is reduced by the expansion valve 14. The refrigerantexpands to obtain a low pressure, is then branched to flow through therefrigerant inlet tubes 16A via the refrigerant pipe 42, and reaches theevaporator 16. It is to be noted that the refrigerant at the inlet ofthe evaporator 16 has a two-phase mixed state in which the liquidrefrigerant is mixed with a vapor refrigerant. Moreover, when theliquid-phase refrigerant absorbs the heat from the milk as the object tobe cooled in the evaporator 16, the refrigerant evaporates to form thevapor refrigerant. At this time, the milk is cooled by the heatabsorption.

Furthermore, the refrigerant evaporated in the evaporator 16 repeats acycle of exiting from the evaporator 16 via the refrigerant outlet tubes16B to combine and enter the suction pipe 45 and being again sucked fromthe low-pressure side to the compressor 10 via the check valve 18 andthe accumulator 17. When the above cycle is repeated, the milk is cooledby the heat absorption of the refrigerant in the evaporator 16.

When the milking is completed, the introduction of the milk into thecooling vessel 7 is completed. However, the above cooling operation iscontinued until the milk reaches a predetermined temperature. Here, thetemperature of the milk is detected by the cooled object temperaturesensor T5 attached to the outer peripheral surface of the inner tank 70.The predetermined temperature at which the cooling operation ends is setfrom a viewpoint that the generation of the bacteria in the milk beinhibited and the quality be maintained, and is specifically about 4° C.

Furthermore, during the cooling operation, an open degree of theexpansion valve 14 is adjusted so that a difference between thetemperature of the refrigerant entering the compressor 10 from theevaporator 16 detected by the sucked refrigerant temperature sensor T7disposed at the suction pipe 45 of the refrigerant circuit 2 and theevaporation temperature of the refrigerant detected by the evaporationtemperature sensor T6 disposed at the evaporator 16 or the refrigerantpipe 42, that is, a so-called superheat degree indicates a predeterminedvalue. That is, when the superheat degree is larger than thepredetermined value, the open degree of the expansion valve 14 isenlarged. Conversely, when the superheat degree is smaller than thepredetermined value, the open degree of the expansion valve 14 isreduced.

It is to be noted that the compressor 10 during the cooling operationmay have the constant number of rotations. Alternatively, a frequencymay be adjusted by an inverter or the like. In the present embodiment, arequired cooling capacity is calculated from a change of the temperatureof the milk with time, the temperature being detected by the cooledobject temperature sensor T5 attached to the outer peripheral surface ofthe inner tank 70, and the number of the rotations of the compressor 10is controlled so as to obtain the operation frequency according to thecalculation result. In consequence, a cooling efficiency can beimproved.

Here, the above control will be described in detail. As described above,the predetermined temperature at which the milk is cooled in the coolingvessel 7 is determined from a viewpoint of the maintenance of thequality of the milk as the object to be cooled. For a similar reason, arequired time for cooling the milk at the predetermined temperature isdetermined. Since a cow farming scale differs with a farm, a device tocool the milk is selected in accordance with each farming scale so as tocomplete the cooling at the predetermined temperature within apredetermined time. However, since a milking amount fluctuates even inthe same farm daily, milk quality control is usually prioritized, andthe refrigeration cycle device having a sufficiently large coolingcapacity is used. Therefore, when the number of the rotations of thedevice during the cooling operation is set to be constant, anexcessively large cooling capacity is required during an actual coolingoperation, and the operation cannot necessarily be said to be efficient.

To solve the problem, in the present embodiment, a cooling speed iscalculated from the change of the temperature of the milk with time,detected by the cooled object temperature sensor T5 attached to theouter portion of the inner tank 70 as described above. The number of therotations of the compressor 10 is adjusted so as to complete the coolingoperation within a preset required cooling time, and the coolingcapacity is controlled. That is, according to a calculation result, in acase where it is judged that a small amount of the milk is to be cooledand that the cooling at the predetermined temperature is completedwithin a time which is shorter than the predetermined required time,control is executed so as to reduce the number of the rotations of thecompressor 10. In consequence, the evaporation temperature can beraised, and the efficiency can be improved. Therefore, while apredetermined cooling capacity is satisfied and the quality of the milkis secured, energy consumption during the cooling operation can bereduced.

It is to be noted that the operation at a frequency at which the highestefficiency is obtained may be prioritized in consideration of theoperation efficiency of the compressor 10, a conversion efficiency ofthe inverter and the like. In this case, the cooling operation issometimes completed within the time shorter than the predeterminedrequired time on conditions that the amount of the milk is sufficientlysmall.

As described above, during the cooling operation of the refrigerationcycle device 1 of the present embodiment, when the milk immediatelyafter drawn is introduced into the cooling vessel 7, the milk can becooled at the predetermined temperature in order to maintain the qualityof the milk.

(2) Operation During Cold Insulating Operation

When the temperature of the milk reaches the predetermined value duringthe above cooling operation, the compressor 10 is stopped, the expansionvalve 14 is completely closed and the stirrer (not shown) is stopped toend the cooling operation, and a cold insulating operation of the milkstored in the cooling vessel 7 is performed. In this case, the coolingvessel 7 is insulated by the insulation material 74 as described above,but the temperature of the milk rises owing to the heat entering fromthe outside during storage for a long time.

To solve the problem, even when the compressor 10 and the like arestopped during the cold insulating operation, the milk temperaturesensor T5 continuously detects the temperature of the milk stored in thecooling vessel 7 (this state will hereinafter be referred to as astandby state). When the milk temperature reaches the predeterminedvalue or more, the cooling operation is started again to cool the milk.Moreover, when the milk is cooled at the predetermined temperature bythe cooling operation during the cold insulating operation, the coolingoperation is stopped, and the device is brought into the standby stateagain. The predetermined temperature at which the cooling operation isstarted during the cold insulating operation is specifically about 4.5°C., and the predetermined temperature at which the cooling operation isstopped is about 4° C.

Moreover, the expansion valve 14 is completely closed in the standbystate in order to prevent a refrigerant backflow from the high-pressureside of the refrigerant circuit 2 to the evaporator 16 and suppress theincoming heat into the milk as the object to be cooled in combinationwith the function of the check valve 18 disposed between the evaporator16 and the accumulator 17 along the suction pipe 45. It is to be notedthat even in a case where a block valve or the like is disposed at thesuction pipe 45 instead of the check valve 18 or at the refrigerant pipe42 or 41 instead of the expansion valve 14 and the block valve is closedin the standby state during the cold insulating operation, a similareffect can be obtained.

Here, it is assumed that the stirrer is driven intermittently at aconstant interval in the standby state during the cold insulatingoperation. It is assumed that a stirring operation is performed for, forexample, two minutes at an interval of 30 minutes. The stirrer isintermittently driven in this manner in order to prevent a disadvantagethat a temperature distribution is stratificationally generated in thecooling vessel 7 owing to a temperature difference of the milk duringcold storage for a long time and that correct temperature measurementcannot be performed.

Since an operation of the refrigerant circuit 2 is similar to the abovecooling operation during the milking, detailed description is omittedhere. It is assumed that during the cold insulating operation, thecompressor 10 is controlled to operate with the number of the rotationswith the best efficiency irrespective of the amount of the milk.

(3) Operation Patterns of Cooling Operation and Cold InsulatingOperation in General Farm

The cooling operation and the cold insulating operation of theintroduced milk during the milking have been described above. Next,operation patterns of the cooling operation and the cold insulatingoperation in a general farm will be described.

In the general farm, the milking is performed about twice or three timesa day. During and after the second milking, the milk immediately afterdrawn is additionally introduced into the cooling vessel 7 in which thecooled and insulated milk is stored. As a result, since the milktemperature in the cooling vessel 7 rises, the cooling operation isstarted. When the temperature reaches the predetermined temperature, thecooling operation is stopped to perform the cold insulating operation asdescribed above.

Moreover, there is a case where the milk is taken out of the coolingvessel 7 (milk cargo collection) every day or every other day.Therefore, from the first milking till the milk cargo collection, thecooling operation and the cold insulating operation of the introducedmilk are repeatedly performed twice to six times.

(4) Regarding Refrigerant Inlet Tubes 16A and Refrigerant Outlet Tubes16B

Next, a relation between sizes and spot pitches of the refrigerant inlettubes 16A and refrigerant outlet tubes 16B, and a relation between thenumber of the refrigerant inlet tubes 16A and the refrigerant outlettubes 16B and the capacity of the cooling vessel 7 will be described inmore detail.

Since carbon dioxide is used as the refrigerant in the refrigerantcircuit 2 of the present embodiment, the refrigerant pressure in theevaporator 16 during the cooling operation is as high as about 3 MPa to5 MPa as compared with a conventional fluorocarbon-based refrigerant.Therefore, a pressure resistance in excess of at least 20 MPa isconsidered to be necessary in consideration of safety during theoperation of the compressor 10. Furthermore, it is preferable to securea pressure resistance of about 25 MPa or more in consideration of apressure rise during stopping of the compressor 10.

Especially, the pressure resistances of the bonded portions of therefrigerant inlet tubes 16A and the refrigerant outlet tubes 16B of theevaporator 16 differ with outer dimensions and the spot pitches of therefrigerant inlet tubes 16A and the refrigerant outlet tubes 16B.Therefore, the dimensions and the spot pitches need to be set so thatthe pressure resistance suitable for the use of carbon dioxide can besecured.

To solve the pressure, a destructive pressure test was conducted usingthe evaporator having variously changed spot pitches. FIG. 7 shows oneexample of a result of the destructive pressure test, the abscissaindicates the spot pitch of each spot welding (an interval between thecenter of the certain secured inner portion 78 and the center of thesecured inner portion 78 adjacent to the certain secured inner portion78, i.e., a distance between spots), and the ordinate shows adestructive pressure. According to the test result shown in FIG. 7, ithas been found that the destructive pressure depends on the spot pitchand that, if the spot pitch exceeds 20 mm, it is difficult to secure thepressure resistance of 25 MPa or more. Therefore, it is preferable toset the spot pitch to 20 mm or less. In the present embodiment, the spotpitch is set to 18.5 mm as described above.

However, here, it has been found that, when a tube having a dimension(especially, an outer diameter) substantially equal to that of therefrigerant pipe 42 or the suction pipe 45 is used as the refrigerantinlet tubes 16A and the refrigerant outlet tubes 16B as in aconventional example, the pressure resistances of the bonded portions ofthe refrigerant inlet tubes 16A and the refrigerant outlet tubes 16Bremarkably deteriorate owing to the heat during the welding. Then, thedestructive pressure test was performed on conditions that shapes andtube dimensions of the refrigerant inlet tubes 16A and the refrigerantoutlet tubes 16B were changed. It has been found that, when the outerdiameter of each of the refrigerant inlet tubes 16A and the refrigerantoutlet tubes 16B is set to be ½ or less of the spot pitch, deteriorationof strength of each bonded portion of the tubes 16A, 16B can beprevented. Therefore, it is assumed in the present embodiment that asthe refrigerant inlet tubes 16A and the refrigerant outlet tubes 16B,the pipe having an outer diameter of φ6.35 mm (¼ inch) and a platethickness of 1.0 mm is used.

Furthermore, even in a case where the refrigerant inlet tubes 16A andthe refrigerant outlet tubes 16B each having an outer diameter smallerthan that of the refrigerant pipe 42 or the suction pipe 45 are used,when one refrigerant inlet tube 16A and one refrigerant outlet tube 16Bare connected to one refrigerant passage of the evaporator as in aconventional case, pressure losses of the refrigerant at the refrigerantinlet and outlet of the evaporator 16 increase. This has incurred thedeterioration of the efficiently of the refrigeration cycle device 1.

To solve the problem, as a result of investigation of the number of therefrigerant inlet tubes 16A, the number of the refrigerant outlet tubes16B and the capacity of the cooling vessel 7, it has been concluded thatit is possible to secure the numbers of the refrigerant inlet tubes 16Aand the refrigerant outlet tubes 16B, which are not less than at least avalue obtained by the following equation (1):NT=6.5×10⁻³ ×V/N  Equation (1),in which NT is the number (tubes) of the refrigerant inlet tubes 16A orthe refrigerant outlet tubes 16B of the evaporator 16, V is a ratedcapacity (L) of the cooling vessel 7 and N is the number of times ofmilking every cargo collection.

Since the evaporator 16 of the present invention performs heat exchangebetween the object to be cooled (the milk) and the refrigerant via theonly inner tank 70, a thermal performance of the refrigerant improves,and a temperature difference between the object to be cooled (the milk)and the refrigerant can remarkably be reduced. As a result, it ispossible to obtain an effect that the evaporation temperature and anevaporation pressure increase and that the efficiency of therefrigeration cycle device 1 improves. However, if the number of therefrigerant inlet tubes 16A or the refrigerant outlet tubes 16B issmaller than that obtained by Equation (1), the pressure losses of therefrigerant at the inlet and the outlet of the evaporator 16 increases,and the efficiency deteriorates. Therefore, the above excellent effectof the thermal performance is offset.

That is, when the pressure losses of the refrigerant in the evaporator16 increase, a suction pressure of the compressor 10 drops, and anamount (a refrigerant circulation amount) of the refrigerant to becirculated through the refrigerant circuit 2 decreases. Therefore, adisadvantage occurs that the cooling capacity of the evaporator 16deteriorates, a pressure difference of the compressor 10 furtherincreases, and the efficiency of the refrigeration cycle device 1deteriorates.

In the present embodiment, the cooling vessel 7 having a rated capacityof 1150 liters is used, and the number of the milking times per cargocollection is twice. Therefore, NT (the number of the refrigerant inlettubes 16A or the refrigerant outlet tubes 16B) calculated from Equation(1) is 3.7, and four refrigerant inlet tubes 16A and four refrigerantoutlet tubes 16B of the evaporator 16 are used. It is to be noted thatin the present embodiment, the evaporator 16 has two paths of therefrigerant passages as described above. Therefore, the refrigerant fromthe refrigerant pipe 42 is branched through the four refrigerant inlettubes 16A, and the refrigerant enters either of two refrigerant passagesof the evaporator 16 from each refrigerant inlet tube 16A. Inconsequence, two refrigerant inlet tubes 16A are connected to onerefrigerant passage, and two refrigerant outlet tubes 16B are similarlyconnected to the passage.

Next, a flow of the refrigerant in one refrigerant passage of theevaporator 16 will be described. The refrigerant entering onerefrigerant passage of the evaporator 16 from two refrigerant inlettubes 16A is combined in the one refrigerant passage, absorbs the heatby the heat exchange between the refrigerant and the object to be cooled(the milk), evaporates, is then branched into two flows to enter therefrigerant outlet tubes 16B, exits from the evaporator 16, and is thencombined to flow through the suction pipe 45.

Next, an area of the outer plate 76 will be described. Since therefrigerant passage space 77 constituted between the inner tank 70 andthe outer plate 76 is the refrigerant passage of the evaporator 16 asdescribed above, it is considered that the area of the outer plate 76 issubstantially equal to a heat conduction area of the evaporator 16.Therefore, the area of the outer plate 76 should be determined inconsideration of a required cooling capacity in accordance with thecapacity of the cooling vessel 7 (the inner tank 70). Specifically, itis preferable to set the area to be not less than an area obtained byEquation (2):A=2×10⁻³ ×V/N  Equation (2),in which A is an area (m²) of the outer plate, V is a rated capacity (L)of the cooling vessel 7, and N is the number of the milking times everycargo collection.

When the area of the outer plate 76 is set to be smaller than the valuecalculated by Equation (2), a temperature difference between the objectto be cooled and the refrigerant in the evaporator 16, and theevaporation pressure drops. As a result, the cooling capacity and theefficiency deteriorate, and an highly efficient cooling operation cannotbe performed.

It is to be noted that, needless to say, the area of the outer plate,that is, the heat conduction area can easily be secured, depending onthe shape of the cooling vessel (the inner tank). In this case, theouter plate having an area larger than the value obtained by Equation(2) may be used. In the present embodiment, as described above, thecooling vessel 7 having a rated capacity of 1150 liters is used, and thenumber of the milking times per cargo collection is twice. Therefore, A(the area of the outer plate 76) calculated from Equation (2) is 1.15.However, the area can further be enlarged in consideration of the shapeof the inner tank 70 of the present embodiment. Therefore, the area ofthe outer plate 76 is set to 1.6 m².

As described above in detail, in the present embodiment, the portions ofthe refrigerant passage space 77 between the inner tank 70 and the outerplate 76 constituting the evaporator 16 are bonded at an interval of 20mm or less in the checkered form or the zigzag form. Therefore, thepressure resistance of the evaporator 16 can be improved withoutincreasing the plate thicknesses of the inner tank 70 and the outerplate 76. The outer diameter of the refrigerant inlet tube 16A whichallows the refrigerant to enter the evaporator 16 is set to be smallerthan that of the refrigerant pipe 42, and ½ or less of the spot pitch.The plurality of refrigerant inlet tubes 16A are connected to therefrigerant passage (the refrigerant passage space 77) of the evaporator16. In consequence, when the refrigerant inlet tubes 16A are connectedto the evaporator 16, the deterioration of the strength of the bondedportion of the refrigerant inlet tube 16A due to the welding can beprevented to the utmost. Moreover, the pressure losses of therefrigerant can be reduced.

Similarly, the outer diameter of the refrigerant outlet tube 16B whichallows the refrigerant to exit from the evaporator 16 is set to besmaller than that of the suction pipe 45, and ½ or less of the spotpitch. Moreover, the plurality of refrigerant outlet tubes 16B areconnected to the refrigerant passage (the refrigerant passage space 77)of the evaporator 16. In consequence, when the refrigerant outlet tubes16B are connected to the evaporator 16, the deterioration of thestrength of the bonded portion of the refrigerant outlet tube 16B due tothe welding can be prevented to the utmost. Moreover, the pressurelosses of the refrigerant can be reduced.

Furthermore, since the pressure resistance of the evaporator 16 can besecured without increasing the plate thicknesses of the inner tank 70and the outer plate 76 constituting the evaporator 16 as describedabove, the heat exchange between the object to be cooled and therefrigerant flowing through the evaporator 16 is performed via the onlyinner tank 70. Therefore, the thermal performance of the evaporator 16can be improved.

As a result, the temperature difference between the object to be cooledand the refrigerant during the cooling operation can further be reduced.In consequence, since the evaporation temperature and the evaporationpressure rise and the refrigerant circulation amount of the refrigerantcircuit 2 increases, the pressure difference can be reduced. Asdescribed above, while the pressure resistance of the heat exchanger(the evaporator 16) is secured in the refrigeration cycle device usingcarbon dioxide, the cooling capacity and the efficiency can be improved.

Embodiment 2

Next, a refrigeration cycle device of another embodiment to which thepresent invention is applied will be described. FIG. 5 is a schematicconstitution diagram of the refrigeration cycle device of the embodimentto which the present invention is applied. The refrigeration cycledevice of the present embodiment cools and insulates milk (an object tobe cooled) immediately after drawn in a cooling vessel. Moreover, thedevice generates hot water by heat obtained by cooling the milk, anduses the hot water in automatic washing of the cooling vessel. It is tobe noted that in the following drawing, components denoted with the samereference numerals as those of FIGS. 1 to 4 produce the same or similarfunction and effect, and detailed description thereof is thereforeomitted. A refrigeration cycle device 200 shown in FIG. 5 is providedwith a refrigerant circuit 2 including a compressor 10, a condenser 21,an expansion valve 14 as a throttling means and an evaporator 16; asecond refrigerant circuit 8 including a second compressor 80, a secondcondenser 81, an expansion valve 84 as a throttling means and anevaporator 86; a hot water supply circuit 3 including a hot waterstorage tank 30; and an automatic washing unit 9 described later.

The refrigerant circuit 2 is constituted so that the compressor 10, thecondenser 21, the expansion valve 14 and the evaporator 16 aresuccessively connected to one another in an annular form via pipes toform a closed circuit. Specifically, a high-pressure refrigerant pipe 40connected to the compressor 10 on a discharge side is connected to aninlet of the condenser 21. The condenser 21 is a refrigerant passageconstituting a part of a heat exchanger 13, and disposed so that heatexchange between the condenser and a water passage 12 of the hot watersupply circuit 3 can be performed. This heat exchanger 13 is a heatexchanger of heat exchange between water and a refrigerant, whichperforms the heat exchange between the condenser 21 and the water storedin the hot water storage tank 30 of the hot water supply circuit 3. Theheat exchanger is constituted of the refrigerant passage as thecondenser 21 and the water passage 12 of the hot water supply circuit 3.One end of the heat exchanger 13 is provided with an inlet of therefrigerant passage of the condenser 21 and an outlet of the waterpassage 12, and the other end of the heat exchanger is provided with anoutlet of the refrigerant passage of the condenser 21 and an inlet ofthe water passage 12. Therefore, in the heat exchanger 13, ahigh-temperature high-pressure refrigerant discharged from thecompressor 10 and flowing through the condenser 21 and the water flowingthrough the water passage 12 form a counterflow.

On the other hand, a refrigerant pipe 41 connected to the outlet of thecondenser 21 is connected to an inlet of the expansion valve 14. Arefrigerant pipe 42 connected to an outlet of the expansion valve 14 isconnected to an inlet of the evaporator 16. Moreover, an outlet of theevaporator 16 is connected to one end of a suction pipe 45, and theother end of the suction pipe 45 is connected to the compressor 10 on alow-pressure side (a suction portion). Along the suction pipe 45 whichconnects the evaporator 16 to the compressor 10 on the low-pressureside, an accumulator 17 is interposed which protects the compressor 10from a disadvantage that a liquid refrigerant is sucked into thecompressor 10 to damage the compressor or the like. Furthermore, at thesuction pipe 45 between the evaporator 16 and the accumulator 17, acheck valve 18 is disposed in which a compressor 10 side (an accumulator17 side) is a forward direction in order to prevent backflow of therefrigerant from a high-pressure side of the refrigerant circuit 2 tothe evaporator 16.

Moreover, a discharge temperature sensor T1 which detects a temperatureof the high-temperature high-pressure refrigerant discharged from thecompressor 10 is disposed at the high-pressure refrigerant pipe 40 ofthe refrigerant circuit 2.

Furthermore, carbon dioxide which is a natural refrigerant is introducedas the refrigerant in the refrigerant circuit 2 in the same manner as inthe refrigerant circuit 2 of Embodiment 1. Moreover, since the pressureof the refrigerant circuit 2 on the high-pressure side rises in excessof a critical pressure, the refrigerant circuit 2 constitutes atrans-critical cycle. As a lubricant of the compressor 10, for example,mineral oil, alkyl benzene oil, ether oil, ester oil, polyalkyleneglycol (PAG), polyol ether (POE) or the like is used.

On the other hand, the evaporator 16 is a heat exchanger which cools theobject to be cooled (the milk in the present embodiment) stored in aninner tank 70 of a cooling vessel 7, and is formed integrally with thiscooling vessel 7. Since a basic constitution of the cooling vessel 7 issimilar to that of the cooling vessel 7 of Embodiment 1 shown in FIGS. 2to 4, detailed description thereof is omitted.

As shown in FIG. 5, the cooling vessel 7 is provided with anintroduction port 7A for introducing the object to be cooled (the milk)and a takeout port (not shown) for taking out the object to be cooled(the milk). An introduction pipe 50 is detachably connected to theintroduction port 7A via an introduction port valve 50B. Furthermore, atakeout pipe 52 for taking out the milk is detachably connected to themilk takeout port via a takeout valve 52B. Moreover, the milkintroduction pipe 50 is attached to the milk introduction port 7A in anonly case where the milk is introduced into the inner tank 70 of thecooling vessel 7. In another case, the pipe is detached from the milkintroduction port 7A, and the milk introduction port 7A is hermeticallyclosed. Similarly, the milk takeout pipe 52 is attached to the milktakeout port in an only case where the milk is taken out of the innertank 70 of the cooling vessel 7. In another case, the pipe is detachedfrom the milk takeout port, and the milk takeout port is hermeticallyclosed.

Moreover, a milk temperature sensor T5 for detecting a temperature ofthe milk as the object to be cooled is attached to an outer peripheralsurface of the inner tank 70 of the cooling vessel 7. Furthermore, thecooling vessel 7 is provided with a stirrer 75 which stirs the milk inorder to promote heat conduction during the cooling and correctlymeasure the temperature with reduced temperature unevenness. The stirrer75 is constituted of a stirring blade, a stirring motor and a shaftwhich connects the blade to the motor.

On the other hand, the second refrigerant circuit 8 is constituted sothat the compressor 80, the condenser 81, the expansion valve 84 and theevaporator 86 are successively connected to one another in an annularform via pipes to form a closed circuit. Specifically, a high-pressurerefrigerant pipe 90 connected to the compressor 80 on the discharge sideis connected to an inlet of the condenser 81. The condenser 81 is arefrigerant passage constituting a part of a heat exchanger 83, anddisposed so that heat exchange between the condenser and a second waterpassage 82 of the hot water supply circuit 3 can be performed. This heatexchanger 83 is a heat exchanger of heat exchange between water and arefrigerant, which performs the heat exchange between the condenser 81and the water stored in the hot water storage tank 30 of the hot watersupply circuit 3. The heat exchanger is constituted of the refrigerantpassage as the condenser 81 and the water passage 82 of the hot watersupply circuit 3. One end of the heat exchanger 83 is provided with aninlet of the refrigerant passage of the condenser 81 and an outlet ofthe water passage 82, and the other end of the heat exchanger isprovided with an outlet of the refrigerant passage of the condenser 81and an inlet of the water passage 82. Therefore, in the heat exchanger83, a high-temperature high-pressure refrigerant discharged from thecompressor 80 and flowing through the condenser 81 and the water flowingthrough the water passage 82 form a counterflow.

On the other hand, a refrigerant pipe 91 connected to the outlet of thecondenser 81 is connected to an inlet of the expansion valve 84. Theexpansion valve 84 is a throttling means to reduce the pressure of therefrigerant which has rejected the heat in the condenser 81, and arefrigerant pipe 92 connected to an outlet of the expansion valve 84 isconnected to an inlet of the evaporator 86. The evaporator 86 is, forexample, a tube and fin type heat exchanger, and constituted of a coppertube and a thermal conduction promoting aluminum fin disposed at thiscopper tube. Moreover, in the copper tube, a channel is constitutedthrough which the refrigerant from the expansion valve 84 flows. In thevicinity of the evaporator 86, a fan 86F and a fan motor 86M whichdrives the fan 86F are installed. The fan supplies, to the evaporator86, atmospheric air (air) as a heat source to be subjected to heatexchange between the air and the refrigerant flowing through the coppertube. It is to be noted that the heat source of the evaporator 86 is notlimited to the atmospheric air, and another heat source such as water,drain, solar heat or underground water may be used.

Moreover, an outlet of the evaporator 86 is connected to one end of asuction pipe 95, and the other end of the suction pipe 95 is connectedto the compressor 80 on the low-pressure side (the suction portion).Along the suction pipe 95 which connects the evaporator 86 to thecompressor 80 on the low-pressure side, an accumulator 87 is interposedwhich protects the compressor 80 from a disadvantage that a liquidrefrigerant is sucked into the compressor 80 to damage the compressor orthe like.

Furthermore, the high-pressure refrigerant pipe 90 of the secondrefrigerant circuit 8 is provided with a discharge temperature sensor T8which detects a temperature the high-temperature high-pressurerefrigerant discharged from the compressor 80.

It is to be noted that carbon dioxide which is a natural refrigerant isintroduced as the refrigerant in the second refrigerant circuit 8 in thesame manner as in the refrigerant circuit 2. Moreover, since thepressure of the second refrigerant circuit 8 on the high-pressure siderises in excess of the critical pressure, the second refrigerant circuit8 constitutes a trans-critical cycle.

On the other hand, the hot water supply circuit 3 is constituted of ahot water storage circuit 5 which receives the heat from the refrigerantflowing through the condenser 21 of the refrigerant circuit 2 or therefrigerant flowing through the condenser 81 of the second refrigerantcircuit 8 to heat the water and generate the high-temperature water andwhich stores the hot water in the hot water storage tank 30; a watersupply unit 32 which supplies water into the hot water storage tank 30;a hot water supply unit 34 which supplies the hot water stored in thehot water storage tank 30 to the automatic washing unit 9 and anotherhot water supply load facility; and a discharge unit 36 described later.

The hot water storage tank 30 is a tank in which the high-temperaturewater generated by the heat rejected from the condenser 21 in the heatexchanger 13 or the condenser 81 in the heat exchanger 83 is stored. Thewhole outer peripheral surface of the tank is covered with an insulationmaterial, and the tank is structured so that the stored hot water doesnot easily cool.

Moreover, a lower portion of the hot water storage tank 30 is connectedto a low-temperature pipe 47 which takes out low-temperature water (thewater) stored in the hot water storage tank 30 from below the hot waterstorage tank 30. The low-temperature pipe 47 is connected to the inletof the water passage 12 formed at the other end of the heat exchanger 13via a circulation pump 31 and a flow rate adjustment valve 35. Thecirculation pump 31 circulates the water through the hot water storagecircuit 5. The circulation pump 31 of the present embodiment dischargesthe water taken from the lower portion of the hot water storage tank 30on a heat exchanger 13 side or a heat exchanger 83 side, and circulatesthe water through the hot water storage circuit 5 so that a water flowin the water passage 12 or 82 of the heat exchanger 13 or 83 forms acounterflow against a refrigerant flow in the condenser 21 or 81 asdescribed above (circulates the water in a clockwise direction in FIG.5). The flow rate adjustment valve 35 is a valve unit which adjusts aflow rate of the warm water circulated through the hot water storagecircuit 5 by the circulation pump 31.

Furthermore, a three-way valve 47A is disposed on an upstream side ofthe circulation pump 31 of the low-temperature pipe 47, and connected toone end of a bypass pipe 49 so that the pipe is branched from thelow-temperature pipe 47 via the three-way valve 47A. The other end ofthe bypass pipe 49 is connected to a middle portion of ahigh-temperature pipe 48. Moreover, the three-way valve 47A can beswitched to thereby selectively switch whether the water is passedthrough the circulation pump 31 from below the hot water storage tank30, or the hot water (the water) passed through the heat exchanger 13 orthe hot water (the water) passed through the heat exchanger 83 is passedthrough the circulation pump 31.

In addition, a three-way valve 47B is disposed on a downstream side ofthe flow rate adjustment valve 35 of the low-temperature pipe 47, andconnected to a low-temperature pipe 97 so that the pipe is branched fromthe low-temperature pipe 47 via the three-way valve 47B. Thelow-temperature pipe 97 is connected to an inlet of the water passage 82formed at the other end of the heat exchanger 83. The three-way valve47B can selectively switch whether the water passed through the flowrate adjustment valve 35 is passed through the heat exchanger 13 or 83.

Moreover, one end of a high-temperature pipe 98 is connected to anoutlet of the water passage 82 formed at one end of the heat exchanger83, and the other end of the high-temperature pipe 98 is connected to amiddle portion of the high-temperature pipe 48.

On the other hand, an outlet of the water passage 12 formed at one endof the heat exchanger 13 is connected to one end of the high-temperaturepipe 48, and the other end of the high-temperature pipe 48 is connectedto an upper portion (an upper end in the present embodiment) of the hotwater storage tank 30. On a downstream side of a connection point ofthis high-temperature pipe 48 to the high-temperature pipe 98, a hotwater temperature sensor T2 is disposed which detects a temperature ofthe high-temperature water generated by the heat rejected from thecondenser 21 in the heat exchanger 13 or the heat rejected from thecondenser 81 in the heat exchanger 83 and entering the hot water storagetank 30.

Moreover, the upper portion of the hot water storage tank 30 isconnected to the high-temperature pipe 48, and provided with ahigh-temperature water takeout port 37 which takes the high-temperaturewater out of the hot water storage tank 30. The high-temperature watertakeout port 37 is connected to a high-temperature water takeout pipe34A of the hot water supply unit 34. The lower portion of the hot waterstorage tank 30 is connected to the low-temperature pipe 47, andprovided with a low-temperature water takeout port 38 which takes thelow-temperature water out of the hot water storage tank 30. Thislow-temperature water takeout port 38 is connected to a low-temperaturewater takeout pipe 34B of the hot water supply unit 34.

Furthermore, the high-temperature water takeout pipe 34A is connected toa washing hot water supply pipe 60, and the high-temperature water takenout of the hot water storage tank 30 via the high-temperature watertakeout port 37 is supplied to the automatic washing unit 9 via thewashing hot water supply pipe 60. The automatic washing unit 9 is a unitfor washing the cooling vessel 7, and the high-temperature water storedin the hot water storage tank 30 is taken from the washing hot watersupply pipe 60 for use as water for washing the cooling vessel 7. Thewashing hot water supply pipe 60 is provided with a check valve 61 forpreventing a disadvantage that the hot water flowing through the washinghot water supply pipe 60 flows back to the hot water storage tank 30;and a water supply valve (a hot water supply valve) 62 for supplying thehot water as the washing water. It is to be noted that although notshown in FIG. 5, the washing hot water supply pipe 60 may be providedwith a temperature sensor which detects a temperature of the hot waterflowing through the washing hot water supply pipe 60; a flow rate sensorwhich detects an amount of the hot water; a flow switch or the like ifnecessary.

In addition, it is assumed in the present embodiment that thehigh-temperature water supplied from the washing hot water supply pipe60 is used in washing the cooling vessel 7. However, the washing hotwater supply pipe 60 may be connected to, for example, a washing unitfor washing a unit such as a milking machine or a milking pipeline otherthan the cooling vessel 7 (not shown: with the proviso that a part ofthe machine or the pipeline is connected to the milk introduction pipe50) to use the hot water in washing the machine or the pipeline.

Moreover, in FIG. 5, a mixture valve 65 mixes the high-temperature watertaken out of the hot water storage tank 30 via the high-temperaturewater takeout pipe 34A with the low-temperature water taken out of thehot water storage tank 30 via the low-temperature water takeout pipe 34Bor the water supplied from the water supply unit 32 via thelow-temperature water takeout pipe 34B, adjusts a temperature of themixed water into an optimum temperature and supplies the water to thehot water supply load facility for use in an application other than thewashing application. The mixture valve 65 is connected to each hot watersupply load facility for use in an application other than the washingapplication. Moreover, the hot water is supplied to the hot water supplyload facility for the application other than the washing application byoperating a hot water supply valve (not shown). The high-temperaturewater takeout pipe 34A and the low-temperature water takeout pipe 34Bconnected to the mixture valve 65 are provided with check valves 67 forpreventing a disadvantage that the hot water taken out of the hot waterstorage tank 30 from the high-temperature water takeout pipe 34A or thelow-temperature water takeout pipe 34B flows back to the hot waterstorage tank 30, respectively.

Furthermore, a hot water supply pipe 68 leading from the mixture valve65 to the hot water supply valve of each hot water supply load facilityis provided with a check valve 68B for preventing the backflow to thehot water storage tank 30; and a temperature sensor T3 for use in hotwater supply control. Moreover, a temperature of the hot water to besupplied to the hot water supply load facility is detected by thetemperature sensor T3. It is to be noted that the hot water supply valveis, for example, a faucet for hot water supply or the like, and thenumber of the valves is not limited to one. A plurality of hot watersupply valves may be disposed. The hot water supply pipe 68 may beprovided with a flow rate sensor and a flow switch (both are not shown)if necessary.

In addition, the lower portion of the hot water storage tank 30 isconnected to a water supply pipe 32A of the water supply unit 32 via apressure reduction valve 32B. The water supply unit 32 supplies waterinto the hot water storage tank 30. Water such as city water having anamount corresponding to an amount of the hot water of the hot waterstorage tank 30 to be used is supplied into the hot water storage tank30 via the water supply pipe 32A. A water supply valve (not shown) isinterposed along this water supply pipe 32A, and the water supply valveis usually constantly brought into an open state.

Moreover, the lower portion of the hot water storage tank 30 isconnected to a discharge pipe 69A via a discharge valve 69B. Thedischarge pipe discharges the hot water from the hot water storage tank30, when the hot water storage tank 30 is unused.

Here, the discharge unit 36 discharges the water (the hot water) fromthe hot water storage tank 30, and is disposed below thehigh-temperature water takeout port 37 and above the low-temperaturewater takeout port 38. In the present embodiment, a hot water dischargepipe 36A of the discharge unit 36 is connected to a portion of the hotwater storage tank 30 below the high-temperature water takeout port 37and above the low-temperature water takeout port 38 via a hot waterdischarge valve 36B. Since the discharge unit 36 is disposed below thehigh-temperature water takeout port 37 and above the low-temperaturewater takeout port 38 in this manner, the hot water taken out of the hotwater storage tank 30 by the discharge unit 36 is medium-temperaturewater having a temperature which is lower than that of the hot watertaken from the high-temperature water takeout port 37 and higher thanthe water taken from the low-temperature water takeout port 38.Therefore, when the hot water discharge valve 36B is opened as needed,the medium-temperature water can be discharged from the hot waterstorage tank 30.

On the other hand, an outer surface of the hot water storage tank 30 isprovided with a plurality of stored hot water sensors T4 arranged atappropriate intervals from the upper portion to the lower portion. Thestored hot water sensors T4 are sensors which detect temperatures ofportions of the hot water stored in the hot water storage tank 30 andwhich detect whether or not there is hot water. Since the plurality ofstored hot water sensors T4 are arranged at varied heights to detect thetemperatures of the portions in this manner, it is possible to detectthe amount of the hot water stored in the hot water storage tank 30while grasping a temperature distribution from the upper portion to thelower portion of the hot water storage tank 30.

It is to be noted that a capacity of the hot water storage tank 30 needsto be determined in due consideration of an amount of the milk as theobject to be cooled, introduced into the cooling vessel 7; and anassumed hot water supply load. That is, during a cooling operation, ifthe high-temperature water is taken from the lower portion of the hotwater storage tank 530 instead of the low-temperature water and thewater enters the water passage 12 of the heat exchanger 13, an amount ofthe heat to be rejected from the condenser 21 remarkably decreases. As aresult, a cooling capacity and COP of the refrigerant circuit 2deteriorate. Therefore, when the capacity of the hot water storage tank30 is considered, the tank should have a sufficient volume so that thelow-temperature water can constantly be taken from the lower portion ofthe hot water storage tank 30, and passed through the water passage 12of the heat exchanger 13.

Specifically, each capacity needs to be investigated individually inaccordance with use conditions. For example, in a case where the hotwater is not used simultaneously with the cooling operation, it ispreferable to use the hot water storage tank having a capacity whichequals or exceeds the maximum amount of the milk as the object to becooled, supposed to be introduced into the cooling vessel 7 during onecooling operation. For example, in a case where 500 liters of the objectto be cooled (the milk) is introduced into the cooling vessel 7, it ispreferable that the capacity of the hot water storage tank 30 equals orexceeds about 500 liters. In a case where it is assumed that the hotwater is used during the cooling operation, the capacity of the hotwater storage tank 30 can be set to be smaller than the above capacity.

Moreover, the automatic washing unit 9 is constituted of a circulationwashing circuit 100 constituted by successively connecting a washingcirculation pump 101, a washing pipe 102, the cooling vessel 7, thetakeout valve 52B, a circulation changeover valve 104 and a washingreturn pipe 105; a washing water discharge passage 110 connected to thewashing return pipe 105 of the circulation washing circuit 100 via awashing discharge valve 110B; and a washing buffer tank 115 connected tothe washing return pipe 105 of the circulation washing circuit 100.

The washing buffer tank 115 is connected to at least one or moredetergent supply pipes 116 for supplying a detergent or a germicide; awater supply pipe 117 for supplying the washing water (the city water inthe present embodiment); and the washing hot water supply pipe 60 forsupplying the hot water for washing from the hot water supply circuit 3.The water supply pipe 117 is provided with a water supply valve 117B,and the water supply to the buffer tank 115 for washing is controlled bythe water supply valve 117B. The detergent supply pipe 116 is providedwith a detergent supply pump (not shown) for supplying the detergent,and the other end of the detergent supply pipe 116 is connected to adetergent vessel (not shown).

An operation of the refrigeration cycle device 200 of the presentembodiment constituted as described above will be described.

(1) Cooling Operation of Object (Milk) to be Cooled

First, an operation to cool the milk as the object to be cooled duringthe cooling operation will be described. The milking pipeline connectedto the milking machine (not shown) is connected to the cooling vessel 7via the milk introduction pipe 50, the introduction port valve 50B isopened, and the milk immediately after drawn is introduced into thecooling vessel 7. At this time, the milk takeout valve 52B is closed. Atemperature of the milk immediately after drawn is substantially equalto or slightly lower than a body temperature of a cow, and isspecifically in a range of about 35° C. to 38° C. Then, the refrigerantcircuit 2 is operated to cool and insulate the milk for the purpose ofpreventing generation of bacteria and maintaining a quality of the milk.

After starting the milking (after starting the introduction of themilk), the compressor 10 of the refrigerant circuit 2 is driven, and thestirrer 75 is simultaneously driven. Usually, it is assumed that after apredetermined amount of milk is stored in the cooling vessel 7, thecompressor 10 is driven to start the cooling operation. However, thecooling operation may be started simultaneously with the start of theintroduction of the milk or before the introduction of the milk as longas careful consideration is given so as to prevent freezing and idlingof the stirrer 75 is prevented.

When the compressor 10 is driven, a low-temperature low-pressurerefrigerant gas is sucked and compressed on the low-pressure side (thesuction portion) of the compressor 10 from the suction pipe 45. Inconsequence, the refrigerant gas which has obtained a high temperatureand a high pressure enters the high-pressure refrigerant pipe 40 fromthe discharge side, and is discharged from the compressor 10. At thistime, the refrigerant is compressed under an appropriate supercriticalpressure.

The high-temperature high-pressure refrigerant discharged from thecompressor 10 enters the heat exchanger 13 from the inlet of thecondenser 21 via the high-pressure refrigerant pipe 40. Moreover, whilepassing through the condenser 21 of the heat exchanger 13, thehigh-temperature high-pressure refrigerant gas releases the heat to thewater of the hot water storage circuit 5 flowing through the waterpassage 12 disposed so as to perform the heat exchange between the waterand the condenser 21. In consequence, the gas obtains a low temperature.On the other hand, the water flowing through the water passage 12 isheated by a heat radiation function of this condenser 21, and thehigh-temperature water is generated.

In the present embodiment, carbon dioxide is used as the refrigerant,and the refrigerant pressure in the condenser 21 is not less than acritical pressure. Therefore, since condensation of the refrigerant doesnot occur in the condenser 21, the temperature of the refrigerantgradually drops from the inlet toward the outlet of the condenser 21 asthe heat is rejected to the water flowing through the water passage 12.On the other hand, from the inlet to the outlet of the water passage 12of the heat exchanger 13, the temperature of the water gradually risesas the heat is absorbed from the refrigerant. Since the refrigerantpressure of the condenser 21 is set to be not less than the criticalpressure by use of the carbon dioxide refrigerant in this manner, theheat exchange can highly efficiently be performed and thehigh-temperature water can be generated as compared with condensationheat radiation of a conventional refrigerant such as an HFC-basedrefrigerant at a constant temperature. In the heat exchanger 13, therefrigerant passage and the water passage 12 constituting the condenser21 are arranged so as to form the counterflow as described above.Therefore, the heat exchange between the water and the refrigerant canfurther efficiently be performed.

The low-temperature high-pressure refrigerant cooled by the condenser 21exits from the heat exchanger 13 via the outlet of the condenser 21,passes through the refrigerant pipe 41, expands at the expansion valve14 to obtain a low pressure and reaches the evaporator 16 via therefrigerant pipe 42. It is to be noted that the refrigerant at the inletof the evaporator 16 has a two-phase mixed state in which the liquidrefrigerant is mixed with a vapor refrigerant. Moreover, when theliquid-phase refrigerant absorbs the heat from the milk as the object tobe cooled in the evaporator 16, the refrigerant evaporates to form thevapor refrigerant. At this time, the milk is cooled by the heatabsorption.

Moreover, the refrigerant evaporated in the evaporator 16 repeats acycle of exiting from the evaporator 16 to enter the suction pipe 45 andbeing again sucked from the low-pressure side (the suction portion) tothe compressor 10 via the check valve 18 and the accumulator 17. Whenthe above cycle is repeated, the milk is cooled by the heat absorptionof the evaporator 16. Moreover, the hot water is generated by the heatrejected from the condenser 21.

When the milking is completed, the introduction of the milk into thecooling vessel 7 is completed. However, the above cooling operation iscontinued until the milk reaches a predetermined temperature. Here, thetemperature of the milk is detected by the milk temperature sensor T5attached to the outer peripheral surface of the inner tank 70. Thepredetermined temperature at which the cooling operation ends is setfrom a viewpoint that the generation of the bacteria in the milk beinhibited and the quality be maintained, and is specifically about 4° C.

Furthermore, an open degree of the expansion valve 14 is adjusted sothat the temperature of the discharged refrigerant detected by thedischarge temperature sensor T1 disposed at the high-pressurerefrigerant pipe 40 of the refrigerant circuit 2 is a predeterminedtemperature during the cooling operation. Specifically, when therefrigerant temperature detected by the discharge temperature sensor T1rises above the predetermined value, the open degree of the expansionvalve 14 is enlarged. Conversely, when the refrigerant temperaturedetected by the discharge temperature sensor T1 drops below thepredetermined value, the open degree of the expansion valve 14 isreduced. In consequence, a highly efficient operation can be performedon conditions preferable for an operation of generating thehigh-temperature water suitable for the washing application.

It is to be noted that the compressor 10 during the cooling operationmay have the constant number of rotations. Alternatively, a frequencymay be adjusted by an inverter or the like. Since the number of therotations is controlled in the same manner as in Embodiment 1 describedabove, detailed description is omitted.

(2) Operation of Hot Water Supply Circuit 3 During Cooling Operation

Next, the operation of the hot water supply circuit 3 during the coolingoperation will be described. First, the three-way valve 47A is switchedso that the water flows through the circulation pump 31 from the lowerportion of the hot water storage tank 30, and the three-way valve 47B isswitched so that the water passed through the flow rate adjustment valve35 flows through the heat exchanger 13 of the refrigerant circuit 2 (therefrigerant circuit 2 for cooling the milk).

Moreover, when the above cooling operation is started, the circulationpump 31 of the hot water supply circuit 3 is started. Thelow-temperature water or the water (hereinafter referred to simply asthe water) is sucked from the lower portion of the hot water storagetank 30 to the circulation pump 31 via the low-temperature pipe 47, andpushed out to the low-temperature pipe 47 connected to the outlet of thecirculation pump 31 on the heat exchanger 13 side. In consequence, thewater pushed out of the circulation pump 31 enters the heat exchanger 13from the inlet of the water passage 12 via the flow rate adjustmentvalve 35. In the heat exchanger 13, as described above, the waterflowing through the water passage 12 receives the heat from thecondenser 21 by the heat exchange between the water and the refrigerantflowing through the condenser 21, and is heated. In consequence, thehigh-temperature water is generated. Moreover, the high-temperaturewater discharged from the heat exchanger 13 via the outlet of the waterpassage 12 passes through the high-temperature pipe 48 of the hot waterstorage circuit 5, and is injected into the hot water storage tank 30from the upper portion (the upper end) of the hot water storage tank 30.The high-temperature water generated by the heat exchanger 13 isinjected into the upper portion of the hot water storage tank 30, andthe water is taken from the lower portion of the tank. Therefore, thehigh-temperature water is stored in an upper part of the tank and thelow-temperature water is stored in a lower part of the tank by use of adensity difference due to a water temperature difference.

Furthermore, the flow rate adjustment valve 35 adjusts the flow rate ofthe water so that the temperature of the hot water at the outlet of thewater passage 12 of the heat exchanger 13 indicates a predeterminedvalue. In the present embodiment, the flow rate adjustment valve 35 iscontrolled based on the temperature of the hot water at the outlet ofthe water passage 12 of the heat exchanger 13 detected by the hot watertemperature sensor T2. That is, when the temperature of the hot water atthe outlet of the water passage 12 detected by the hot water temperaturesensor T2 is higher than the predetermined temperature, the open degreeof the flow rate adjustment valve 35 is enlarged. In consequence, anamount (the flow rate) of the water to be circulated through the hotwater storage circuit 5 can be increased.

On the other hand, when the temperature of the hot water at the outletof the water passage 12 detected by the hot water temperature sensor T2is lower than the predetermined temperature, the open degree of the flowrate adjustment valve 35 is reduced. In consequence, the amount (theflow rate) of the water to be circulated through the hot water storagecircuit 5 can be reduced. It is to be noted that in the presentembodiment, the temperature of the hot water at the outlet of the waterpassage 12 is detected by the hot water temperature sensor T2 installedat the middle portion of the high-temperature pipe 48. However, thepresent invention is not limited to this example. Needless to say, thetemperature of the hot water at the outlet of the water passage 12 maybe detected by a temperature sensor disposed at the outlet of the waterpassage 12 of the heat exchanger 13. It is preferable to set thepredetermined temperature to a temperature suitable for an applicationof hot water supply (including a washing application), specifically in arange of about 50° C. to 85° C. in accordance with a use application.

As described above, during the cooling operation of the refrigerationcycle device 200 of the present embodiment, when the milk immediatelyafter drawn is introduced into the cooling vessel 7, the milk is cooledat the predetermined temperature in order to maintain the quality of themilk. Moreover, the high-temperature water is generated by the heatrejected from the refrigerant circuit 2 on the high-pressure side, andthe hot water can be stored in the hot water storage tank 30.

(3) Operation During Cold Insulating Operation

In the refrigeration cycle device 200, when the temperature of the milkreaches the predetermined value during the above cooling operation, acold insulating operation to insulate the milk is executed in the samemanner as in the refrigeration cycle device 1 of Embodiment 1. Sinceoperation conditions, an operation method and the like during the coldinsulating operation are similar to those of Embodiment 1, detaileddescription thereof is omitted. A function of the refrigerant circuit 2,an operation of the hot water supply circuit 3 and the like during thecold insulating operation are similar to those during the above coolingoperation. It is to be noted that in the refrigeration cycle device 200of the present embodiment, even in the cooling operation during the coldinsulating operation, simultaneously with the cooling of the milk, thehot water can be stored by effectively using discharged heat during thecooling.

It is to be noted that since operation patterns of the cooling operationand the cold insulating operation in a general farm are the same asdescribed above in Embodiment 1, detailed description thereof isomitted.

(4) Washing Operation

Next, a washing operation will be described. As described above, themilk cooled and insulated in the cooling vessel 7 as described above istaken from the takeout port during the milk cargo collection.Specifically, the milk takeout valve 52B is connected to the milktakeout pipe 52, the milk takeout valve 52B is opened and the milk istaken out of the cooling vessel 7. Moreover, after the milk is takenout, the washing operation is performed by the automatic washing unit 9in order to keep the inside of the cooling vessel 7 to be clean, inhibitpropagation of the bacteria and secure the quality of the milk.

Usually, the washing of the cooling vessel 7 is performed after takingthe milk out of the cooling vessel 7. Therefore, in a case where thecargo is collected every day, the washing is performed once a day. Whenthe cargo is collected every other day, the washing is performed onceevery two days. In the present embodiment, the hot water for washing canbe supplied even for the washing of the milking machine or the milkingpipeline (not shown). However, since the milking machine and the milkingpipeline are washed every time the milking is completed, the washing isperformed twice or three times a day.

Washing steps in a case where the cooling vessel 7 is washed arebasically the same as those in a case where the milking pipeline or thelike is washed. That is, a rinsing step with the water, a rinsing stepwith the hot water, a washing step with a plurality of types ofdetergents such as an alkaline detergent and an acid detergent and asterilization step with a germicide are performed. In each of suchsteps, the hot water or the water is supplied, predetermined amounts ofpredetermined types of detergent and germicide are supplied, then awashing liquid (a mixture liquid of the hot water or the water and thedetergent and the like) is circulated through the device (through thecirculation washing circuit 100 in a case where the cooling vessel 7 iswashed) for a predetermined time if necessary, and the washing liquid isthen discharged.

Moreover, the above steps are performed in a predetermined order thenecessary number of times. For example, first the rinsing step with thewater is performed. Subsequently, another rinsing step with the hotwater, an alkali washing step with the hot water and the alkalinedetergent, still another rinsing step with the hot water, an acidwashing step with the hot water and the acid detergent and a furtherrinsing step with the water are performed. Subsequently, thesterilization step with the germicide is performed.

When the milk cargo collection is completed, prior to the washing, firstthe milk takeout pipe 52 is detached from the takeout valve 52B so thatthe washing water flows through the washing return pipe 105 via thetakeout valve 52B, and the takeout valve 52B is opened. In the rinsingstep with the water, the discharge valve 110B for washing and thecirculation changeover valve 104 are closed, and the circulation pump101 for washing is stopped. In this state, the water supply valve 117Bis opened, and the predetermined amount of the washing water is suppliedto the buffer tank 115 for washing via the water supply pipe 117. It isto be noted that it can be judged with, for example, a floating typelevel switch or the like whether or not an amount of the water in thebuffer tank 115 for washing reaches a predetermined value.

Moreover, when the amount of the water in the buffer tank 115 forwashing reaches the predetermined value, the water supply valve 117B isclosed, and the circulation pump 101 is brought into an operative state.In consequence, the water passes through the washing pipe 102 from thebuffer tank 115 for washing, and is supplied into the cooling vessel 7.To inject the water into the cooling vessel 7 from the washing pipe 102,the water is jetted from nozzles and sprayed into each portion of thecooling vessel 7 without unevenness so that efficient washing can beperformed. If necessary, the stirrer 75 may be operated.

If the water in the buffer tank 115 for washing is used up, theoperation of the circulation pump 101 for washing is stopped, thecirculation changeover valve 104 and the discharge valve 110B forwashing are opened, and the rinsing water is discharged from the washingwater discharge passage 110. One rinsing step with the water has beendescribed above. The predetermined number of the steps are repeatedlyperformed as needed.

On the other hand, the rinsing step with the hot water is basically anoperation similar to that of the above rinsing step with the water, andis different only in that the high-temperature water is supplied insteadof the water. That is, in the rinsing step with the water, the watersupply valve 117B is opened to supply the water. However, in the rinsingstep with the hot water, the hot water supply valve 62 is opened tothereby supply the high-temperature water stored in the hot waterstorage tank 30 to the buffer tank 115 for washing via the hot watersupply pipe 60 for washing. Description of another similar operation isomitted.

In the washing step with the detergent, the discharge valve 110B forwashing and the circulation changeover valve 104 are closed, and thecirculation pump 101 for washing is stopped. In this state, the watersupply valve 62 is opened, and a predetermined amount of the hot wateris supplied to the buffer tank 115 for washing via the hot water supplypipe 60 for washing. Moreover, a detergent supply pump (not shown) isdriven to supply the predetermined amount of the predetermined type ofdetergent to the buffer tank 115 for washing via the detergent supplypipe 116. The type and the amount of the supplied detergent aredetermined beforehand in accordance with the steps, and the amount ofthe detergent is adjusted in accordance with a driving time of thedetergent supply pump (not shown).

Moreover, when the amount of the hot water (the mixture liquid of thehot water and the detergent) in the buffer tank 115 for washing reachesa predetermined value, the water supply valve 62 is closed, and thecirculation pump 101 is brought into the operative state. Inconsequence, the detergent passes through the washing pipe 102 from thebuffer tank 115 for washing, and is supplied into the cooling vessel 7.To inject the washing liquid into the cooling vessel 7 from the washingpipe 102, the washing liquid is jetted from nozzles and sprayed intoeach portion of the cooling vessel 7 without unevenness so that theefficient washing can be performed. If necessary, the stirrer 75 may beoperated.

If the washing liquid in the buffer tank 115 for washing is used up, theoperation of the circulation pump 101 for washing is stopped. Thecirculation changeover valve 104 and the discharge valve 110B forwashing remain to be closed until the predetermined amount of thewashing liquid is stored in the cooling vessel 7. The water supply valve62 is opened again, and the predetermined amount of the hot water issupplied into the buffer tank 115 for washing. Subsequently, the watersupply valve 62 is closed, the circulation pump 101 is driven, and thehot water is supplied into the cooling vessel 7. This operation isrepeated. Here, the amount of the hot water supplied and stored in thecooling vessel 7 can be known from the capacity of the buffer tank 115and the number of the repeated operations. Therefore, in a case wherethe number of the times when the hot water is stored in the buffer tank115 is determined beforehand, an appropriate amount can be controlled.

After the predetermined amount of the washing liquid (the mixture liquidof the hot water and the detergent) is stored in the cooling vessel 7,the circulation changeover valve 104 is opened, and the circulation pump101 for washing is driven for a predetermined time. The washing liquidfrom the cooling vessel 7 successively flows through the takeout valve52B, the circulation changeover valve 104, the washing return pipe 105,the washing circulation pump 101 and the washing pipe 102 to return tothe cooling vessel 7, and circulates through the circulation washingcircuit 100. In consequence, dirt of the milk in the cooling vessel 7can be removed. It is to be noted that to inject the washing liquid intothe cooling vessel 7 from the washing pipe 102, the washing liquid isjetted from nozzles and sprayed into each portion of the cooling vessel7 without unevenness so that efficient washing can be performed. Ifnecessary, the stirrer 75 may be operated.

Moreover, after the washing liquid is circulated for a predeterminedtime, the circulation pump 101 for washing is stopped, the dischargevalve 110B for washing is opened, and the washing liquid is dischargedfrom the circulation washing circuit 100 via the discharge passage 110for washing.

An operation of the sterilization step is basically similar to that ofthe washing step with the detergent, and is different only in that thedetergent to be injected is the germicide, the water is used instead ofthe hot water and a different time for circulation or the like is set.The sterilization step is performed in accordance with the next usetime, and a germicide liquid (a mixture liquid of the germicide and thewater) is held in systems of the cooling vessel 7 and the circulationwashing circuit 100 and left to stand for a predetermined time toimprove a sterilization effect. Detailed description of an operationcommon to that of the rinsing step or the washing step with thedetergent is omitted.

It is to be noted that in the standby state of the cold insulatingoperation, the expansion valve 14 is completely closed in order toreduce thermal losses due to the entering refrigerant in the evaporator16. However, during the washing operation, especially when the washingwith the hot water is performed, it is preferable to bring the expansionvalve 14 into an open state in order to avoid an abnormally highpressure in the evaporator 16.

Moreover, in a case where a large hot water supply load is required andthe supply of the only amount of the hot water generated by cooling themilk is insufficient, the hot water may be generated by performing thecooling operation even during the washing operation. For example, in thesterilization step, while the germicide liquid is held in the coolingvessel 7, the cooling operation is performed. In consequence, a hotwater supply operation (a heat pump operation) can highly efficiently beperformed using the germicide liquid as a heat source. Furthermore, ifnecessary, the water can additionally be introduced as the heat sourceinto the cooling vessel 7 to perform the cooling operation (the hotwater supply operation).

(5) Hot Water Supply Operation for Application Other than WashingApplication

Next, an operation of supplying the hot water to an application otherthan the above washing application will be described. The hot water issupplied to a hot water supply load for the application other than thewashing application by opening the hot water supply valve. When the hotwater supply valve is opened, the high-temperature water stored in thehot water storage tank 30 flows through the mixture valve 65 from theupper portion of the hot water storage tank 30 via the high-temperaturewater takeout pipe 34A. Moreover, the water from the water supply unit32, or the low-temperature water from the lower portion of the hot waterstorage tank 30 flows through the mixture valve 65 via thelow-temperature water takeout pipe 34B connected to the lower portion ofthe hot water storage tank 30. Moreover, the mixture valve 65 mixes thehigh-temperature water and the water or the low-temperature water. Afterthe temperature is adjusted into a predetermined temperature, the hotwater is supplied to each hot water supply load facility via the hotwater supply valve.

It is to be noted that the temperature of the hot water to be suppliedis detected by the temperature sensor T3 disposed at the pipe 68 whichconnects the mixture valve 65 to the hot water supply valve. It is to benoted that since the water supply valve (not shown) of the water supplyunit 32 is usually constantly opened, the city water having an amountcorresponding to the amount of the hot water supplied to another hotwater supply load facility (the hot water supply load facility otherthan the automatic washing unit 9) is supplied into the hot waterstorage tank 30 of the hot water supply circuit 3 from the water supplypipe 32A of the water supply unit 32.

As described above, according to the refrigeration cycle device 200 ofthe present embodiment, at the same time the milk as the object to becooled is cooled, the hot water is generated by effectively using theheat of the high-temperature side of the refrigerant circuit 2 generatedin the cooling process. Moreover, the high-temperature water can besupplied by using the trans-critical cycle by use of the carbon dioxiderefrigerant. This hot water can be used in washing the cooling vessel 7and the like. Therefore, as compared with a conventional case in whichthe water is boiled with a boiler or the like to supply the hot waterfor the washing application, energy to be consumed can largely bereduced. Since the heat released from the high-temperature side of therefrigerant circuit 2 to the atmospheric air can be reduced, a rise ofan ambient temperature can be inhibited.

(6) Hot Water Supply Operation by Use of Second Refrigerant Circuit 8

Next, an operation of the second refrigerant circuit 8 will bedescribed. The second refrigerant circuit 8 is disposed so as to performa hot water supply operation (the heat pump operation) of absorbing theheat from a heat source such as air other than the milk in a case wherea large hot water supply load is required and the supply of the only hotwater obtained by cooling the milk is insufficient.

Since the operation of the second refrigerant circuit 8 is substantiallythe same as that of the refrigerant circuit 2, detailed descriptionthereof is omitted. The operation is different from that of therefrigerant circuit 2 only in that the refrigerant in the evaporator 86absorbs the heat from the atmospheric air. That is, in the evaporator86, the refrigerant absorbs the heat from the atmospheric air, and theheat is rejected to the water passage 82 disposed so that the heatexchange between the water and the condenser 81 is performed in the heatexchanger 83. In consequence, the water flowing through the waterpassage 82 is heated, and the high-temperature water is generated.

During the hot water supply operation, the open degree of the expansionvalve 84 is adjusted so that the temperature of the dischargedrefrigerant detected by the discharge temperature sensor T8 disposed atthe high-pressure refrigerant pipe 90 of the second refrigerant circuit8 indicates a predetermined value. Specifically, when the refrigeranttemperature detected by the discharge temperature sensor T8 rises abovethe predetermined value, the open degree of the expansion valve 84 isenlarged. Conversely, when the refrigerant temperature detected by thedischarge temperature sensor T8 drops below the predetermined value, theopen degree of the expansion valve 84 is reduced. In consequence, ahighly efficient operation can be performed on conditions preferable foran operation of generating the high-temperature water suitable for thewashing application.

Next, an operation of the hot water supply circuit 3 during the hotwater supply operation will be described. In this case, the three-wayvalve 47A is switched so that the water flows through the circulationpump 31 from the lower portion of the hot water storage tank 30, and thethree-way valve 47B is switched so that the water passed through theflow rate adjustment valve 35 flows through the heat exchanger 83.During the hot water supply operation, the circulation pump 31 of thehot water supply circuit 3 is operated, and the low-temperature water orthe water from the lower portion of the hot water storage tank 30 flowsthrough the low-temperature pipe 47, the circulation pump 31, the flowrate adjustment valve 35 and the low-temperature pipe 97 to enter theinlet of the water passage 82 of the heat exchanger 83. In the heatexchanger 83, as described above, the water flowing through the waterpassage 82 is heated by the heat exchange between the water and therefrigerant flowing through the condenser 81 to generate thehigh-temperature water. Moreover, the high-temperature water exitingfrom the water passage 82 of the heat exchanger 83 successively flowsthrough the high-temperature pipes 98 and 48, and is injected into thehot water storage tank 30 from the upper portion of the hot waterstorage tank 30. The high-temperature water is injected from the upperportion of the hot water storage tank 30, and the low-temperature wateris taken from the 5 lower portion of the tank. Therefore, thehigh-temperature water is stored in an upper part of the hot waterstorage tank 30 and the low-temperature water is stored in a lower partof the tank by use of a density difference due to a water temperaturedifference.

Moreover, the flow rate adjustment valve 35 adjusts the flow rate of thewater so that the temperature of the hot water at the outlet of thewater passage 82 of the heat exchanger 83 indicates a predeterminedvalue. Specifically, when the temperature of the hot water at the outletof the 15 water passage 82 is higher than the predetermined temperature,the open degree of the flow rate adjustment valve 35 is enlarged toincrease the flow rate of the water. Conversely, when the temperature ofthe hot water at the outlet of the water passage 82 is lower than thepredetermined temperature, the open degree of the flow rate adjustmentvalve 35 is reduced to decrease the flow rate of the water. Thetemperature of the hot water at the outlet of the water passage 82 isdetected by the hot water temperature sensor T2 attached to thehigh-temperature pipe 48. Moreover, the predetermined temperature is atemperature suitable for the washing application or another hot watersupply application. Specifically, it is preferable to set thetemperature in a range of about 50 to 85° C. in accordance with a useapplication.

As described above, the hot water supply operation of the secondrefrigerant circuit 8 is performed in a case where the amount of the hotwater generated by the milk cooling operation falls short with respectto the required hot water supply load. A length of time when the hotwater supply operation is performed, that is, the amount of the hotwater to be generated is determined in accordance with the requiredamount of the hot water. However, when the hot water storage tank 30 iscompletely filled with the high-temperature water, the high-temperaturewater flows through the heat exchanger 13 from the lower portion of thehot water storage tank 30 during the cooling operation. The coolingcapacity and efficiency remarkably deteriorate, and it is difficult tocool the milk. Therefore, during the hot water supply operation, the hotwater storage tank 30 is not completely filled with the high-temperaturewater, and it is necessary to surely secure a cold water portion (aportion of water having a low temperature) having an amountcorresponding to an amount for use during the cooling operation in thelower part of the hot water storage tank 30.

The amount of the hot water to be stored in the hot water storage tank30 during the hot water supply operation of the second refrigerantcircuit 8 depends on conditions on which the refrigeration cycle device200 is used, that is, the amount (a farming scale) of the milk, theamount of the hot water for use and the like. For example, when theamount of the hot water is ⅕ or less of that in the hot water storagetank 30, the hot water supply operation is started by the secondrefrigerant circuit 8. When the amount is ½ or more, the hot watersupply operation of the second refrigerant circuit 8 is stopped. Suchcontrol is considered. It is to be noted that the amount of the hotwater stored in the hot water storage tank 30 can be grasped by thestored hot water sensors T4.

As described above, the refrigeration cycle device 200 of the presentembodiment includes the second refrigerant circuit 8. Therefore, whenthe required hot water supply load cannot be covered only with the hotwater generated during the cooling of the milk, the hot water supplyoperation is performed using the atmospheric air as the heat source. Inconsequence, the hot water can be generated to compensate for shortage.Therefore, an auxiliary boiler or the like for the additional hot watersupply is not required. Moreover, heat pump hot water supply is highlyefficiently performed. Therefore, energy consumption is further reduced.

(7) Changeover Operation of Three-Way Valve 47A

Next, an operation of the three-way valve 47A will be described. Thethree-way valve 47A prevents the low-temperature water from being passedthrough the upper portion of the hot water storage tank 30 to disturbthermal stratification in the hot water storage tank 30 during thestarting and stopping of the cooling operation and the hot water supplyoperation. For a predetermined time TL1 after the start of the coolingoperation or the hot water supply operation, the three-way valve 47A isblocked on a hot water storage tank 30 side, and switched so as to passthe hot water (or the water) through the circulation pump 31 from thebypass pipe 49. In consequence, for the predetermined time TL1 from thestart of the cooling operation or the hot water supply operation, thehot water passed through the water passage 12 of the heat exchanger 13or the water passage 82 of the heat exchanger 83 of the secondrefrigerant circuit 8 does not enter the hot water storage tank 30. Thehot water flows through the closed circuit from the high-temperaturepipe 48 via the bypass pipe 49, the three-way valve 47A and thecirculation pump 31 to return to the water passage 12 of the heatexchanger 13 or the water passage 82 of the heat exchanger 83 of thesecond refrigerant circuit 8.

In addition, for a predetermined time TL2 from the start of the coolingoperation or the hot water supply operation, the open degree of the flowrate adjustment valve 35 is fixed to a predetermined open degree so asto secure a sufficient flow rate. After elapse of the predetermined timeTL2, the open degree is gradually reduced to decrease the flow rate.Finally, the open degree is adjusted so that the hot water temperaturesensor T2 attached to the high-temperature pipe 48 indicates thepredetermined value.

After elapse of the predetermined time TL1, the three-way valve 47A isblocked on a bypass pipe 49 side, and switched so as to pass the waterthrough the circulation pump 31 from the lower portion of the hot waterstorage tank 30. As a result, the hot water generated by the waterpassage 12 of the heat exchanger 13 or the water passage 82 of the heatexchanger 83 of the second refrigerant circuit 8 enters the hot waterstorage tank 30.

As the predetermined times TL1 and TL2, a certain time may be determinedbeforehand. Alternatively, the operation may be performed based on thetemperature of the hot water at the outlet of the heat exchanger 13 orthe heat exchanger 83 of the second refrigerant circuit 8, detected bythe hot water temperature sensor T2. That is, at the start of thecooling operation, the flow rate adjustment valve 35 is fixed to thepredetermined open degree. When the hot water temperature rises to apredetermined value or more, the open degree of the flow rate adjustmentvalve 35 is gradually reduced. Furthermore, when the hot watertemperature rises to a second predetermined temperature, the three-wayvalve 47A may be blocked on the bypass pipe 49 side, and switched so asto pass the water through the circulation pump 31 from the lower portionof the hot water storage tank 30.

As described above, it is possible to avoid a problem that the thermalstratification of the hot water already stored in the hot water storagetank 30 is disturbed to lower the temperature of the stored hot water.As a result, the thermal loss of the stored hot water can be reduced,and the hot water can effectively be used.

Moreover, as described above, the flow rate adjustment valve 35 is fixedto the predetermined open degree so that the sufficient flow rate can besecured for the predetermined time TL2 after the start of the coolingoperation or the hot water supply operation. In consequence, it ispossible to avoid an abnormal discharge temperature rise and anabnormally high pressure immediately after the compressor 10 (or thecompressor 80) is started.

On the other hand, even immediately after the stopping of the coolingoperation or the hot water supply operation, when a predetermined timeelapses after the stopping of the operation of the compressor 10 (or thecompressor 80) or the hot water indicates the predetermined value orless, the three-way valve 47A is blocked on the hot water storage tank30 side, and switched so as to pass the hot water (or the water) throughthe circulation pump 31 from the bypass pipe 49. Subsequently, thecirculation pump 31 is operated for a predetermined time. Inconsequence, the hot water passed through the water passage 12 of theheat exchanger 13 or the water passage 82 of the heat exchanger 83 ofthe second refrigerant circuit 8 does not enter the hot water storagetank 30. The hot water flows through the closed circuit from thehigh-temperature pipe 48 via the bypass pipe 49, the three-way valve 47Aand the circulation pump 31 to return to the water passage 12 of theheat exchanger 13 or the water passage 82 of the heat exchanger 83 ofthe second refrigerant circuit 8.

Therefore, it is possible to prevent the low-temperature water frombeing passed from the upper portion of the hot water storage tank 30into the hot water storage tank 30 to disturb the thermal stratificationin the hot water storage tank 30. Moreover, the heat exchanger 13 or theheat exchanger 83 of the second refrigerant circuit 8 can appropriatelybe cooled.

It is to be noted that, when the usual cooling operation or hot watersupply operation is performed except during the starting and stopping,the three-way valve 47A is blocked on the bypass pipe 49 side, andswitched so as to pass the water through the circulation pump 31 fromthe lower portion of the hot water storage tank 30. When the coolingoperation or the hot water supply operation is not performed, thethree-way valve 47A is blocked on the hot water storage tank 30 side,and switched so as to communicate on the bypass pipe 49 side. When thecooling operation or the hot water supply operation is not performed,the valve is switched to the above state. In consequence, in a casewhere the high-temperature water is supplied to the washing applicationor the like, it is possible to avoid a problem that the cold waterentering the lower portion of the hot water storage tank 30 from thewater supply unit 32 flows through the hot water storage circuit 5 onthe heat exchanger 13 side or the side of the heat exchanger 83 of thesecond refrigerant circuit 8 to enter the upper portion of the hot waterstorage tank 30 and lower the temperature of the hot water to besupplied.

(8) Operation of Discharge Unit 36

In addition, in the refrigeration cycle device 200, a disadvantageoccurs that the excessively large amount of the high-temperature wateris stored in the hot water storage tank 30 owing to increase of thecooling load during the cooling operation or decrease of a hot watersupply load, then the temperature of the hot water taken from the lowerportion of the hot water storage tank 30 also rises and consequently thehigh-temperature water enters the heat exchanger 13.

When the high-temperature water enters the heat exchanger 13, in thecondenser 21 of the heat exchanger 13, the amount of the heat to berejected from the refrigerant flowing through the condenser 21 to thewater flowing through the water passage 12 remarkably drops or fallsshort. In consequence, since the refrigerant cannot be cooled at a lowtemperature in the condenser 21, a problem occurs that a specificenthalpy of the refrigerant flowing through the evaporator 16 rises, acooling capacity of the evaporator 16 and the efficiency of therefrigeration cycle device 200 remarkably deteriorate and the cooling ofthe object to be cooled in the evaporator 16 is hindered.

To solve such a problem, according to the refrigeration cycle device 200of the present embodiment, in a case where the temperature of the waterstored in the hot water storage tank 30, the temperature of the water tobe circulated through the heat exchanger 13 for the heat exchangebetween the condenser 21 and the water stored in the hot water storagetank 30, the temperature in the condenser 21 or the temperature of therefrigerant discharged from the condenser 21 rises to a predeterminedvalue or more, the discharge unit 36 discharges the water from the hotwater storage tank 30.

Here, an operation of discharging the water from the hot water storagetank 30 by the discharge unit 36 will be described. It is assumed thatin the refrigeration cycle device 200 of the present embodiment, whenthe temperature of the water to be circulated through the heat exchanger13 for the heat exchange between the condenser 21 and the water storedin the hot water storage tank 30 rises to a predetermined value or more,for example, 25° C. to 30° C. or more, the water is discharged from thehot water storage tank 30 by the discharge unit 36. It is to be notedthat the temperature at which the water is discharged from the hot waterstorage tank 30 by the discharge unit 36 is not limited to thetemperature of the water to be circulated through the heat exchanger 13for the heat exchange between the condenser 21 and the water stored inthe hot water storage tank 30 as in the present embodiment. Thetemperature may be the temperature of the water stored in the hot waterstorage tank 30, detected by the stored hot water sensors T4, thetemperature of the refrigerant in the condenser 21 of the heat exchanger13 or the temperature of the refrigerant discharged from the condenser21.

Moreover, it is assumed that the hot water discharge valve 36B disposedat the hot water discharge pipe 36A of the discharge unit 36 is usuallyclosed, and in this state the water is not discharged from the hot waterstorage tank 30 via the hot water discharge pipe 36A.

Furthermore, during the cooling operation, when the temperature (thetemperature of the water at the inlet of the water passage 12 of theheat exchanger 13) of the water to be circulated through the heatexchanger 13 for the heat exchange between the condenser 21 and thewater stored in the hot water storage tank 30 rises to the predeterminedvalue or more, the hot water discharge valve 36B of the hot waterdischarge pipe 36A is opened. In consequence, the medium-temperaturewater having a temperature which is lower than that of the hot watertaken from the high-temperature water takeout port 37 of the hot waterstorage tank 30 and higher than the water taken from the low-temperaturewater takeout port 38 is discharged from the hot water storage tank 30via the hot water discharge pipe 36A.

Simultaneously with the discharge of the hot water via the hot waterdischarge pipe 36A, the amount of cold water corresponding the amount ofthe discharged hot water is supplied into the hot water storage tank 30from the water supply pipe 32A of the water supply unit 32. It is to benoted that the hot water discharged from the hot water storage tank 30via the hot water discharge pipe 36A may be used for an appropriateapplication if any.

When the hot water is discharged from the hot water storage tank 30 viathe hot water discharge pipe 36A and the amount of the cold watercorresponding to the amount of the discharged hot water issimultaneously supplied into the hot water storage tank 30 in thismanner, the temperature of the hot water stored in the lower part of thehot water storage tank 30 can be lowered. The hot water stored in thelower part of the hot water storage tank 30 and having the loweredtemperature, or the cold water supplied into the hot water storage tank30 by the water supply unit 32 can be supplied to the heat exchanger 13.

In consequence, in the heat exchanger 13, it is possible to secure theamount of the heat rejected from the refrigerant, required for theevaporator 16 to maintain the cooling function. That is, in the heatexchanger 13, the heat of the refrigerant flowing through the condenser21 is sufficiently released to the water flowing through the waterpassage 12, and the temperature of the refrigerant can be lowered.Therefore, the cooling capacity of the evaporator 16 can be maintainedand the object to be cooled can securely be cooled.

Embodiment 3

It has been described in the above embodiments (Embodiments 1 and 2)that a cooling vessel 7 having a horizontally disposed elliptic columnarshape is used as a vessel to cool and insulate an object to be cooled.However, as described above, the shape of the cooling vessel may beanother shape. Therefore, in the present embodiment, a case where acooling vessel having a columnar shape is used will be described. It isto be noted that the present embodiment is different from the aboveembodiments only in the shape of the cooling vessel. Therefore, an onlydifferent constitution will be described. Since another constitution isthe same as or similar to that of the above embodiments, descriptionthereof is omitted.

FIG. 6 is a schematic constitution diagram of an evaporator 316 of thepresent embodiment as viewed from a bottom surface of an inner tank 370.A cooling vessel 307 of the present embodiment has a vertically disposedcolumnar shape, a bottom surface 370B (the other plate material) of theinner tank 370 substantially has a circular shape. An outer plate 376(one plate material) secured to the bottom surface 370B substantiallyhas a circular shape.

As shown in FIG. 6, the whole periphery of a peripheral portion of theouter plate 376 is secured to the bottom surface 370B of the inner tank370 by seam welding, a sealed refrigerant passage space 377 isconstituted between the plate materials (between the bottom surface 370Bof the inner tank 370 and the outer plate 376), and this space is usedas a refrigerant channel of the evaporator 316.

Moreover, a portion of the outer plate 376 other than the peripheralportion is provided with a plurality of secured inner portions 378secured to the bottom surface 370B of the inner tank 370 atpredetermined intervals. Specifically, the whole periphery of theperipheral portion of the outer plate 376 is secured to the bottomsurface of the inner tank 370 by the seam welding, and the portion otherthan the peripheral portion is secured with spot at predeterminedintervals in a checkered form or a zigzag form by spot welding (portionssecured by the spot welding are the secured inner portions 378).

Furthermore, a plurality of refrigerant inlet tubes 316A and refrigerantoutlet tubes 316B are attached to the refrigerant passage space 377 (arefrigerant channel of the evaporator 316) formed between the bottomsurface 370B of the inner tank 370 and the outer plate 376. Moreover, asshown in FIG. 6, one end of each of the plurality of refrigerant inlettubes 316A communicates with the refrigerant passage space 377 in thecenter of the refrigerant passage space 377, and one end of eachrefrigerant outlet tube 316B communicates with the refrigerant passagespace 377 in the peripheral portion of the refrigerant passage space377.

The refrigerant inlet tubes 316A have an arrangement concentric with theouter plate 376 substantially having a circular shape, and are connectedto the center of the refrigerant passage space 377 at substantiallyequal intervals. The refrigerant outlet tubes 316B have an arrangementconcentric with the outer plate 376 substantially having a circularshape, and are connected to the peripheral portion of the refrigerantpassage space 377 at substantially equal intervals.

On the other hand, the other end of the refrigerant inlet tube 316A isconnected to a refrigerant pipe 42 so that the refrigerant from therefrigerant pipe 42 is branched to flow through the refrigerant passagespace 377. Moreover, the other end of the refrigerant outlet tube 316Bis connected to a suction pipe 45 so that the refrigerants from therefrigerant outlet tubes 316B are combined.

Moreover, even in the present embodiment, in the same manner as in theabove embodiments, the inner tank 370 has a plate thickness of 2 mm, andthe outer plate 376 has a plate thickness of 1 mm. Spot-welded portions(the secured inner portion 78) have a diameter of 6 mm, and a spot pitchof 18.5 mm. The refrigerant inlet tubes 316A and the refrigerant outlettubes 316B have an outer diameter of φ6.35 mm (¼ inch), and therefrigerant inlet tubes 316A and the refrigerant outlet tubes 316B havea plate thickness of 1.0 mm.

As described above in Embodiment 1, the number of the refrigerant inlettubes 316A or the refrigerant outlet tubes 316B, and an area of theouter plate 376 can be calculated from Equations (1) and (2) describedabove. IN the present embodiment, the cooling vessel 307 having a ratedcapacity of 1000 liters is used, and the number of milking times percargo collection is two. Therefore, NT (the number of the refrigerantinlet tubes 316A or the refrigerant outlet tubes 316B of the evaporator316) calculated from Equation (1) is 3.25, and four refrigerant inlettubes 316A and four refrigerant outlet tubes 316B are used. Since A (thearea of the outer plate 376) calculated from Equation (2) is 1, an areaof the outer plate 376 is set to 1.13 m² of the present embodiment.

In the present embodiment, the evaporator 316 has one path, fourrefrigerant inlet tubes 316A and four refrigerant outlet tubes 316B.Therefore, the refrigerant from the refrigerant pipe 42 is branched intofour flows, flows through the refrigerant inlet tubes 316A, and entersthe refrigerant passage (the center of the refrigerant passage space 77)of the evaporator 316 from each refrigerant inlet tube 316A. Moreover,the refrigerants entering the center of the evaporator 316 from therefrigerant inlet tubes 316A are once combined in the evaporator 316,and flows from the center in a circumferential direction. In thisprocess, the refrigerant absorbs heat by heat exchange between therefrigerant and the object to be cooled and evaporates. The evaporatedrefrigerant is branched into four flows to enter the refrigerant outlettubes 316B, flows out of the evaporator 316 via the refrigerant outlettubes 316B, and is combined to flow through the suction pipe 45.

As described above in detail, in the evaporator 316 of the presentembodiment, the refrigerant inlet tubes 316A communicate with therefrigerant passage space 377 in the center of the refrigerant passagespace 377. Moreover, the refrigerant outlet tubes 316B communicate withthe refrigerant passage space 377 in the peripheral portion of therefrigerant passage space 377. Therefore, the refrigerant entering theevaporator 316 from the vicinity of the center flows so as to spread inthe circumferential direction. It is therefore possible to inhibit adisadvantage that pressure losses increase as the refrigerantevaporates.

That is, as the refrigerant evaporates, a specific volume increases.Therefore, in a case where the area of the refrigerant passage is set tobe equal from a refrigerant inlet to an outlet of the evaporator 316, asthe refrigerant evaporates, the pressure losses increase. However, as inthe present embodiment, the refrigerant inlet tubes 316A are arranged inthe center of the refrigerant passage space 377, and the refrigerantoutlet tubes 316B are arranged in the peripheral portion of therefrigerant passage space 377. In consequence, a refrigerant passagearea of the evaporator 316 is smallest at the inlet of the evaporator316, gradually increases toward the outlet, and is maximized at theoutlet of the evaporator 316. Therefore, such pressure losses canfurther be reduced.

Furthermore, according to such a structure, a branching property of therefrigerant improves. Therefore, stagnation of the refrigerant in theevaporator 316 can be prevented, and improvement of a thermalperformance can be expected.

It is to be noted that it is assumed in each embodiment that the heatexchanger of the present invention is used as the evaporator. However,the present invention is not limited to this example. The heat exchangermay be used as a condenser. When the heat exchanger of the presentinvention is used as the condenser, a heat exchange capability of thecondenser can be enhanced.

Moreover, as the invention that can be grasped from the abovedescription, in addition to the inventions described in claims, thefollowing is considered. That is, the first invention is also directedto a heat exchanger characterized in that after the whole periphery ofthe peripheral portion of the one plate material is secured to the otherplate material, a pressure is applied between the plate materials tothereby swell and form the refrigerant passage space between the platematerials.

The present invention is usable in not only the device which cools andinsulates the milk immediately after drawn as in the above embodimentsbut also another industrial field such as a device related to processingof food and the like or an automatic dispenser in which cooling and coldstorage are demanded.

1. A heat exchanger comprising: a pair of plate materials, wherein thewhole periphery of a peripheral portion of at least one of the platematerials is secured to the other plate material to constitute a sealedrefrigerant passage space between the plate materials; a portion of theone plate material other than the peripheral portion is provided with aplurality of secured inner portions which are secured at predeterminedintervals to the other plate material; and a plurality of refrigerantinlet tubes and refrigerant outlet tubes are attached so as tocommunicate with the refrigerant passage space.
 2. The heat exchangeraccording to claim 1, wherein the secured inner portions are arranged atthe predetermined intervals in a checkered form or a zigzag form.
 3. Theheat exchanger according to claim 1 or 2, wherein the refrigerant inlettubes communicate with the refrigerant passage space in the center ofthe refrigerant passage space; and the refrigerant outlet tubescommunicate with the refrigerant passage space in a peripheral portionof the refrigerant passage space.
 4. A refrigeration cycle devicecomprising: a refrigerant circuit including a compressor, a condenser, athrottling means and an evaporator, wherein the heat exchanger accordingto any one of claims 1 to 3 is used as the evaporator; carbon dioxide isintroduced as a refrigerant; and a supercritical pressure is obtained ona high-pressure side.
 5. The refrigeration cycle device according toclaim 4, wherein the surface of the other plate material opposite to theone plate material constitutes a wall surface of a predetermined spaceto be cooled; and the surface of the one plate material opposite to theother plate material is provided with a predetermined insulationstructure.